# Encyclopedia

.Radioactive decay is the process in which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation.^ At each step in the decay process, radiation is released.
• DrHomeAir.com - Radon FAQ 25 January 2010 17:43 UTC www.drhomeair.com [Source type: FILTERED WITH BAYES]
• Radon - NSC 25 January 2010 17:43 UTC www2.nsc.org [Source type: FILTERED WITH BAYES]

^ Particle decays are like radioactive decays of atomic nuclei.

^ Radioactive decay is the process by which radioactive atoms release energy and or particles to become more stable.
• What's the difference between Nuclear Fission and Radioactive decay? - Yahoo!7 Answers 25 January 2010 17:43 UTC au.answers.yahoo.com [Source type: General]

.This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, named the daughter nuclide.^ As time passes, more of the parent will decay to its daughter nuclides.

^ Each count represents one atom that has decayed.

^ The disintegration of radioactive atoms is called radioactive decay.
• Radioactive Decay 25 January 2010 17:43 UTC classes.mhcc.edu [Source type: Reference]

.For example: a carbon-14 atom (the "parent") emits radiation and transforms to a nitrogen-14 atom (the "daughter").^ Radioactive material is just another name for a group of unstable atoms that emit ionizing radiation.
• Radiation Basics | Radiation Information and Answers 25 January 2010 17:43 UTC www.radiationanswers.org [Source type: FILTERED WITH BAYES]

^ A Z] > m [ A (Z+1)] (Parent atom) > (Daughter atom) .

^ The parent nucleus then becomes the neutral atom [ A Z] plus the mass of one electron, while the daughter nucleus and the beta particle on the right side of the equation become the neutral atom [ A (Z+1)] plus the mass of the beta particle.

.This is a stochastic process on the atomic level, in that it is impossible to predict when a given atom will decay,[1] but given a large number of similar atoms the decay rate, on average, is predictable.^ This is a random process on the atomic level, in that it is impossible to predict when a given atom will decay, but given a large number of similar atoms, the decay rate, on average, is predictable.
• A Strange Connection: Could Nuclear Decay Rates be Influenced by Distance From the Sun? | Astroengine.com 25 January 2010 17:43 UTC www.astroengine.com [Source type: FILTERED WITH BAYES]

^ The atomic number of the decaying nucleus changes its atomic number by a predictable amount.
• How does nuclear fission reactions differ from natural radioactive decay? - Yahoo!7 Answers 25 January 2010 17:43 UTC au.answers.yahoo.com [Source type: General]

^ The rate of decay is proportional to the number of parent atoms present.
• Radiometric Dating 25 January 2010 17:43 UTC facstaff.gpc.edu [Source type: Reference]

.The SI unit of activity is the becquerel (Bq).^ The unit of measure for Radiation is the becquerel (Bq).
• Radioactive Decay - Toxipedia 25 January 2010 17:43 UTC www.toxipedia.org [Source type: FILTERED WITH BAYES]

^ SI unit is becquerel - US unit is curie .
• Radioactive Material Equations Formulas Calculator - Decay Nuclei Number 25 January 2010 17:43 UTC www.ajdesigner.com [Source type: Academic]

^ The unit of activity in the International System (SI) of units is the becquerel (Bq), which is equal to the unit reciprocal second (s -1 ).
• NIST: Ionizing Radiat. Div. - Glossary of Terms 25 January 2010 17:43 UTC physics.nist.gov [Source type: Academic]

.One Bq is defined as one transformation (or decay) per second.^ An activity of one becquerel means one decay per second.

^ (Bq) - Unit of activity equal to one nuclear transformation per second (1 Bq = 1/s).
• http://www.pnl.gov/env/appendix_b.html 25 January 2010 17:43 UTC www.pnl.gov [Source type: Academic]

^ Decay rates, which are measured as particle detections per second, require a time standard that precisely divides time into well defined intervals.
• Alternate View--Analog 25 January 2010 17:43 UTC www.analogsf.com [Source type: Academic]
• Analog Science Fiction & Fact Magazine 25 January 2010 17:43 UTC www.npl.washington.edu [Source type: Academic]

.Since any reasonably-sized sample of radioactive material contains many atoms, a Bq is a tiny measure of activity; amounts on the order of GBq (gigabecquerel, 1 x 109 decays per second) or TBq (terabecquerel, 1 x 1012 decays per second) are commonly used.^ (Bq) means 1 count per second .
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

^ A unit of radioactivity equal to 3.7 x 10 10 disintegrations per second.
• Indoor Radon and Radon Decay Product Measurement Device Protocols - Glossary 25 January 2010 17:43 UTC www.p2pays.org [Source type: Academic]

^ A commonly used measurement is the half-life of a radioactive substance.
• Radioactive Decay 25 January 2010 17:43 UTC classes.mhcc.edu [Source type: Reference]

.Another unit of radioactivity is the curie, Ci, which was originally defined as the amount of radium emanation (radon-222) in equilibrium with of one gram of pure radium, isotope Ra-226. At present it is equal, by definition, to the activity of any radionuclide decaying with a disintegration rate of 3.7 × 1010 Bq.^ A unit of radioactivity equal to 3.7 x 10 10 disintegrations per second.
• Indoor Radon and Radon Decay Product Measurement Device Protocols - Glossary 25 January 2010 17:43 UTC www.p2pays.org [Source type: Academic]

^ One curie is defined as the activity of 1g of radium-226, which is around 37 billion becquerels.

^ Many radioactive materials disintegrate at a rate proportional to the amount present.
• Radioactive decay 25 January 2010 17:43 UTC www.sosmath.com [Source type: FILTERED WITH BAYES]

The use of Ci is presently discouraged by the SI.

## Explanation

The trefoil symbol is used to indicate radioactive material.
.The neutrons and protons that constitute nuclei, as well as other particles that may approach them, are governed by several interactions.^ It includes alpha and beta particles as well as proton and neutron radiation.

^ Particle radiation includes alpha and beta particles as well as proton and neutron radiation.
• Radioactive Decay 25 January 2010 17:43 UTC www.windows.ucar.edu [Source type: FILTERED WITH BAYES]

^ All Uranium atoms contain 92 protons but the sum of the number of protons and neutrons in naturally occuring Uranium can have several different values including 238 and 235 .

.The strong nuclear force, not observed at the familiar macroscopic scale, is the most powerful force over subatomic distances.^ The strong nuclear force , not observed at the familiar macroscopic scale, is the most powerful force over subatomic distances.

^ Neutron radiation is also made from nuclear reactors in power plants and nuclear-powered ships and in particle accelerators, devices used to study subatomic physics.
• HowStuffWorks "How Nuclear Radiation Works" 25 January 2010 17:43 UTC science.howstuffworks.com [Source type: FILTERED WITH BAYES]

^ An improved knowledge of such interactions is also pivotal to emerging technologies such as nanofabrication, nuclear waste management, fusion power and long distance space travel.
• Keeping track of the damage 25 January 2010 17:43 UTC www.aps.anl.gov [Source type: Academic]

.The electrostatic force is almost always significant, and in the case of beta decay, the weak nuclear force is also involved.^ The electrostatic force is also significant.

^ Free neutrons decay slowly via the weak nuclear force.
• radioactive particle concept from the Astronomy knowledge base 25 January 2010 17:43 UTC www.site.uottawa.ca:4321 [Source type: FILTERED WITH BAYES]

^ As beta decay is the classic weak nuclear process, and the only one that occurs at low energy, precision measurements of beta decay continue to be done to refine the limits of the theory.
• beta decay@Everything2.com 25 January 2010 17:43 UTC www.everything2.com [Source type: FILTERED WITH BAYES]

.The interplay of these forces produces a number of different phenomena in which energy may be released by rearrangement of particles.^ The interplay of these forces is very complex.

^ Because of this, sometimes these other processes are used to model the decay process; in the animation shown above, we used a random number generator to determine when each particle would decay.

^ P) in high atomic number materials such as lead may result in the production of secondary radiation (Br�msstrahlung) which is more penetrating than the beta radiation that produced it.
• Radioactive Materials | Guidance | Radiation | Environmental Health & Safety | University Operations Services | Harvard University 3 February 2010 18:018 UTC www.uos.harvard.edu [Source type: Academic]

.Some configurations of the particles in a nucleus have the property that, should they shift ever so slightly, the particles could rearrange into a lower-energy arrangement and release some energy.^ Some configurations of the particles in a nucleus have the property that, should they shift ever so slightly, the particles could fall into a lower- energy arrangement.

^ The spontaneous transition of an atomic nucleus to a lower energy state (radioactive decay) accompanied by the emission of an alpha particle , a beta particle , or gamma radiation .

^ Such an unstable nucleus like Uranium, when gently tapped by a neutron, splits up into two other nuclei through nuclear fission, releasing tremendous amount of energy in the process!
• List of Radioactive Elements 25 January 2010 17:43 UTC www.buzzle.com [Source type: FILTERED WITH BAYES]

.One might draw an analogy with a snowfield on a mountain: while friction between the ice crystals may be supporting the snow's weight, the system is inherently unstable with regard to a state of lower potential energy.^ One might draw an analogy with a tower of sand : while friction between the sand grains can support the tower's weight, a disturbance will unleash the force of gravity and the tower will collapse.

^ The spontaneous transition of an atomic nucleus to a lower energy state (radioactive decay) accompanied by the emission of an alpha particle , a beta particle , or gamma radiation .

^ If an atom emits a gamma ray, or photon, it does not transmutate but transforms itself from an unstable excited energy state into a lower, more stable one.
• Lab 3 - Radioactive Decay 25 January 2010 17:43 UTC www.sethi.org [Source type: FILTERED WITH BAYES]

.A disturbance would thus facilitate the path to a state of greater entropy: the system will move towards the ground state, producing heat, and the total energy will be distributable over a larger number of quantum states.^ The validation of questions go beyond this element in a new framework?:) "Dyson, one of the most highly-regarded scientists of his time, poignantly informed the young man that his findings into the distribution of prime numbers corresponded with the spacing and distribution of energy levels of a higher-ordered quantum state."

^ As it happens, NASA has a number of space probes that match this description, because many space probes, particularly those that venture into the outer reaches of the solar system, are powered by radioisotope-driven thermoelectric power sources containing a strong radioactive decay source that produces enough energy as heat to power the vehicle.
• Alternate View--Analog 25 January 2010 17:43 UTC www.analogsf.com [Source type: Academic]

^ I don't see how it could be an average of the decay over that time, either, since a larger number of atoms would change the time it takes for half to decay.
• Not understanding radioactive decay in Chem class 25 January 2010 17:43 UTC www.geekstogo.com [Source type: General]
• Not understanding radioactive decay in Chem class 25 January 2010 17:43 UTC www.geekstogo.com [Source type: General]

Thus, an avalanche results. .The total energy does not change in this process, but because of the law of entropy, avalanches only happen in one direction and that is towards the "ground state" – the state with the largest number of ways in which the available energy could be distributed.^ The only way that this can happen is by changing the number of protons in the nucleus (an element is defined by its number of protons).
• Radioactive Decay 25 January 2010 17:43 UTC serc.carleton.edu [Source type: FILTERED WITH BAYES]

^ There are a number of ways that this can happen and when it does, the atom is forever changed.
• Radioactive Decay 25 January 2010 17:43 UTC serc.carleton.edu [Source type: FILTERED WITH BAYES]

^ A nucleus will decay if there is a set of particles with lower total mass that can be reached by any of the above types of decay process or simply by fission, a process in which a massive nucleus splits into two less massive ones.  Alpha decay is also a type of fission, common because the alpha particle is a particularly low energy arrangement of two protons and two neutrons.
• Theory: Radioactive Decays (SLAC VVC) 25 January 2010 17:43 UTC www2.slac.stanford.edu [Source type: Original source]

.Such a collapse (a decay event) requires a specific activation energy.^ Such a collapse (a decay event ) requires a certain activation energy .

^ This is because radioactive decay occurs only when it is energetically favorable and requires no outside input of energy.
• Re: Is stopping radioactive decay possible? 25 January 2010 17:43 UTC www.madsci.org [Source type: FILTERED WITH BAYES]

^ The process which results in the change ot an isotope of one element into an isotope of a different element by the emission of energy during spontaneous radioactive decay or the absorption of energy during activation .
• Glossary - T 25 January 2010 17:43 UTC www.spwla.org [Source type: Reference]

.For a snow avalanche, this energy comes as a disturbance from outside the system, although such disturbances can be arbitrarily small.^ A large percentage of it comes from outside of our solar system and is found throughout space.
• Natural Radioactivity 3 February 2010 18:018 UTC physics.isu.edu [Source type: Academic]

^ If the system is modified such that the scintillant is a crystal placed outside of the sample chamber (vial) then the instrument becomes a gamma counter.
• Appendix H: Radioactive tracers 3 February 2010 18:018 UTC homepages.gac.edu [Source type: FILTERED WITH BAYES]

.In the case of an excited atomic nucleus, the arbitrarily small disturbance comes from quantum vacuum fluctuations.^ In the case of an atomic nucleus, it is already present.

^ Similar to an excited atom emitting a photon of visible light when converting back to the ground state, the decay of the exited nucleus comes along with the emission of a γ photon.

^ Any nucleus can be written in a form like this: where Al is the element (aluminum in this case), the 27 is the atomic mass number (the number of neutrons plus the number of protons), and the 13 is Z, the atomic number, the number of protons.
• Radioactive decay 25 January 2010 17:43 UTC physics.bu.edu [Source type: FILTERED WITH BAYES]
• Radioactive decay and radioactivity 25 January 2010 17:43 UTC physics.bu.edu [Source type: FILTERED WITH BAYES]

.A radioactive nucleus (or any excited system in quantum mechanics) is unstable, and can thus spontaneously stabilize to a less-excited system.^ Radioactivity results from the random and spontaneous breakdown of the unstable nucleus of an atom.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ The spontaneous transition of an atomic nucleus to a lower energy state (radioactive decay) accompanied by the emission of an alpha particle , a beta particle , or gamma radiation .

^ Radioactive decay is the spontaneous emission of one or more particles ( alpha particles or beta particles ) or emission of electromagnetic wave ( gamma rays ) from a radioactive nucleus.

.The resulting transformation alters the structure of the nucleus and results in the emission of either a photon or a high-velocity particle which has mass (such as an electron, alpha particle, or other type).^ Alpha particles are a type of ionizing radiation .
• What are alpha rays? How are they... 25 January 2010 17:43 UTC education.jlab.org [Source type: FILTERED WITH BAYES]

^ Alpha particle ( a ) decay-emission of helium particle: .
• Learn Chemistry Tutorials - Nuclear Chemistry Tutorial 25 January 2010 17:43 UTC learnchem.net [Source type: Reference]

^ Shortly after Becquerel discovered the existence of radioactivity , it was shown that there were three types of radioactive emission: positively-charged alpha particles , negatively-charged beta particles , and neutral gamma rays .
• beta decay@Everything2.com 25 January 2010 17:43 UTC www.everything2.com [Source type: FILTERED WITH BAYES]

## Discovery

.Radioactivity was first discovered in 1896 by the French scientist Henri Becquerel, while working on phosphorescent materials.^ Radioactivity was discovered in 1896 by French physicist Henri Becquerel.
• USGS Geology in the Parks 25 January 2010 17:43 UTC geomaps.wr.usgs.gov [Source type: Reference]

^ The unit of radioactivity is named after Henri Becquerel, who discovered it .
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

^ Radioactivity was discovered in 1896 by Henri Becquerel.
• Radiometric Dating 25 January 2010 17:43 UTC facstaff.gpc.edu [Source type: Reference]

.These materials glow in the dark after exposure to light, and he thought that the glow produced in cathode ray tubes by X-rays might be connected with phosphorescence.^ For a time it was thought that these materials were all members of the actinide series ; however, exacting radiochemical research has demonstrated that certain of the light elements also have naturally occurring isotopes that are radioactive.
• radioactive isotope Facts, information, pictures | Encyclopedia.com articles about radioactive isotope 3 February 2010 18:018 UTC www.encyclopedia.com [Source type: Academic]

^ A more likely cause was her exposure to unshielded X-ray tubes while a volunteer medical worker in WWI. .
• The Rocky State of Your Campaign #14: Death by Rock, Part Two - RPGnet 25 January 2010 17:43 UTC www.rpg.net [Source type: FILTERED WITH BAYES]

^ These highly energetic, extremely small-wavelength electromagnetic rays pass right through most physical substances at the speed of light.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

.He wrapped a photographic plate in black paper and placed various phosphorescent salts on it.^ In 1896, Bequerel, a French physicist discovered that crystals of Uranium salts emitted penetrating rays similar to X-rays which could fog photographic plates.
• Radioactivity 25 January 2010 17:43 UTC www.splung.com [Source type: FILTERED WITH BAYES]

^ A gamma source is placed inside the pipe and photographic paper wrapped around the weld.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ He identified a previously unknown type of radiation being emitted from uranium salts, which could fog a photographic plate.

.All results were negative until he used uranium salts.^ Thorium was first used as a nuclear fuel in the 1960s in light-water reactors, and was used as an alternative to uranium fuel in Oak Ridge National Laboratory's Molten Salt Reactor .
• Using Thorium as a Nuclear Fuel: A Less Hazardous Alternative to Conventional Nuclear Power Plants 25 January 2010 17:43 UTC engineering.suite101.com [Source type: FILTERED WITH BAYES]

^ In some areas of the USA, mining companies use chemical solutions pumped into the ground to wash out uranium salts.
• Natural Radioactive Minerals - Survival Unlimited .com 3 February 2010 18:018 UTC www.survivalunlimited.com [Source type: FILTERED WITH BAYES]

^ Unstable nuclides, such as uranium-238, start series of disintegrations that continue until a stable nucleus results.
• Radioactive Decay Part 1 25 January 2010 17:43 UTC www.math.duke.edu [Source type: FILTERED WITH BAYES]
• decay 25 January 2010 17:43 UTC www.math.jmu.edu [Source type: Academic]

The result with these compounds was a deep blackening of the plate. .These radiations were called Becquerel Rays.^ These gamma-rays are called annihilation radiation.
• ARPANSA - Other types of radioactive decay 25 January 2010 17:43 UTC www.arpansa.gov.au [Source type: FILTERED WITH BAYES]

^ Gamma radiation Most radioactive elements emit from the nucleus electromagnetic radiation called gamma rays.
• Isotopes for Medicine and the Life Sciences 25 January 2010 17:43 UTC www.nap.edu [Source type: Academic]

^ The health hazard from these X-rays is sometimes far more acute than the hazard from the alpha or beta radiation of the nuclear transformation itself.
• Radiation Notes: Alpha and Beta Decay 25 January 2010 17:43 UTC oak.cats.ohiou.edu [Source type: FILTERED WITH BAYES]

.It soon became clear that the blackening of the plate had nothing to do with phosphorescence, because the plate blackened when the mineral was in the dark.^ It soon became clear that the Earth was much older than many of the earlier methods indicated.

.Non-phosphorescent salts of uranium and metallic uranium also blackened the plate.^ Becquerel discovered that uranium salts were able to blacken a photographic plate placed in the dark, even through a paper barrier.
• What is Radioactivity? 3 February 2010 18:018 UTC www.wisegeek.com [Source type: FILTERED WITH BAYES]

^ In 1896, Bequerel, a French physicist discovered that crystals of Uranium salts emitted penetrating rays similar to X-rays which could fog photographic plates.
• Radioactivity 25 January 2010 17:43 UTC www.splung.com [Source type: FILTERED WITH BAYES]

^ The Abrams tanks are constructed with a layer of radioactive uranium metal plates.

.Clearly there was a form of radiation that could pass through paper that was causing the plate to become black.^ Becquerel discovered that uranium salts were able to blacken a photographic plate placed in the dark, even through a paper barrier.
• What is Radioactivity? 3 February 2010 18:018 UTC www.wisegeek.com [Source type: FILTERED WITH BAYES]

^ Unfortunately the radiation passes through the 'good' tissue too and kills or damages 'good' cells.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ When alpha or beta particles, or gamma radiation pass through matter, they form ions.
• Appendix H: Radioactive tracers 3 February 2010 18:018 UTC homepages.gac.edu [Source type: FILTERED WITH BAYES]

.At first it seemed that the new radiation was similar to the then recently discovered X-rays.^ Acute effects of radiation were first observed in the use of X-rays when electric engineer Nikola Tesla intentionally subjected his fingers to X-rays in 1896.
• The Rocky State of Your Campaign #14: Death by Rock, Part Two - RPGnet 25 January 2010 17:43 UTC www.rpg.net [Source type: FILTERED WITH BAYES]

^ Radioactivity was first discovered in 1896 by the French scientist Henri Becquerel, after which the SI unit for radiation, the Becquerel , is named.
• What is Radioactivity? 3 February 2010 18:018 UTC www.wisegeek.com [Source type: FILTERED WITH BAYES]

^ Apr 16 - Seeded by Killfile Source: russiatoday.ru Russian geologists have discovered a new mineral which absorbs radiation from liquid nuclear waste.
• Newsvine - radioactive 3 February 2010 18:018 UTC www.newsvine.com [Source type: News]

.Further research by Becquerel, Marie Curie, Pierre Curie, Ernest Rutherford and others discovered that radioactivity was significantly more complicated.^ How people like Marie Curie and Ernest Rutherford etc.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ What two elements were discovered by Marie and Pierre Curie?
• Science NetLinks: Radioactive Decay: A Sweet Simulation of a Half-life 25 January 2010 17:43 UTC www.sciencenetlinks.com [Source type: FILTERED WITH BAYES]

^ Marie Curie was the first woman to win a Nobel Prize and the first person to win two (the first, shared with her husband Pierre and Becquerel for discovering radioactivity; the second for discovering the radioactive elements radium and polonium).

.Different types of decay can occur, but Rutherford was the first to realize that they all occur with the same mathematical approximately exponential formula (see below).^ This is an exponential type of decay not a linear decay.
• Not understanding radioactive decay in Chem class 25 January 2010 17:43 UTC www.geekstogo.com [Source type: General]

^ First of all, what is a radioactive decay?
• Radioactive Decay | Universe Today 25 January 2010 17:43 UTC www.universetoday.com [Source type: FILTERED WITH BAYES]

^ Here again, we see that different decays will occur at different rates: .
• Dealing with Creationism in Astronomy: Accelerated Radioactive Decay? 25 January 2010 17:43 UTC homepage.mac.com [Source type: FILTERED WITH BAYES]

.The early researchers also discovered that many other chemical elements besides uranium have radioactive isotopes.^ HighBeam Research radioactive isotope on Wikipedia .
• radioactive isotope Facts, information, pictures | Encyclopedia.com articles about radioactive isotope 3 February 2010 18:018 UTC www.encyclopedia.com [Source type: Academic]

^ Isotopes are the same chemical element.

^ Many other consumer products are also radioactive.
• How do we detect nuclear materials at the border? - By Daniel Engber - Slate Magazine 3 February 2010 18:018 UTC www.slate.com [Source type: General]

.A systematic search for the total radioactivity in uranium ores also guided Marie Curie to isolate a new element polonium and to separate a new element radium from barium.^ The probability of a process taking place inside of an atomic nucleus, such as radioactive decay of radium, was shown to be the same in all substances containing that element.
• radioactive decay, electron capture, Be7, cold fusion, transmutations, lenr, cmns 25 January 2010 17:43 UTC pages.csam.montclair.edu [Source type: Academic]

^ Marie Curie was the first woman to win a Nobel Prize and the first person to win two (the first, shared with her husband Pierre and Becquerel for discovering radioactivity; the second for discovering the radioactive elements radium and polonium).

^ The discovery of the natural radioactive decay of uranium in 1896 by Henry Becquerel, the French physicist, opened new vistas in science.
• Geologic Time: Radiometric Time Scale 25 January 2010 17:43 UTC pubs.usgs.gov [Source type: FILTERED WITH BAYES]
• Lesson 31A: Using Radioactive Decay to Determine Geologic Age 25 January 2010 17:43 UTC education.gsfc.nasa.gov [Source type: FILTERED WITH BAYES]

.The two elements' chemical similarity would otherwise have made them difficult to distinguish.^ Here are two examples of specific radioactive decay processes: (a)  (b) In both cases, the notation means X is the chemical symbol for the element, A is the number of nucleons (protons and neutrons), and Z is the number of protons.

^ With the loss of two protons and two neutrons, the atom has chemically become a different element than what it was before the emission of the alpha particle.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ Materials made from nuclei all with a single atomic number are known as chemical elements , or simply elements .
• Open Course : Astronomy : Introduction : Lecture 7 : Nature of Matter 25 January 2010 17:43 UTC www.opencourse.info [Source type: FILTERED WITH BAYES]

## Danger of radioactive substances

The danger classification sign of radioactive materials
.
Ionizing radiation hazard symbol (recently introduced).
^ This effect is the reason why ionizing radiation is hazardous to health, and provides the means by which radiation can be detected.

^ Non ionizing radiations are not energetic enough to ionize atoms and interact with materials in ways that create different hazards than ionizing radiation.  Examples of non ionizing radiation include:   .

[2]
.
Alpha particles may be completely stopped by a sheet of paper, beta particles by aluminum shielding.
^ While alpha particles can be stopped by a sheet of paper and beta particles , by an aluminum plate, gamma particles can only be stopped by a thick dense material such as lead.
• Radioactive Decay | Universe Today 25 January 2010 17:43 UTC www.universetoday.com [Source type: FILTERED WITH BAYES]

^ By contrast, alpha and beta particles can be stopped by lighter materials.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ Alpha particles are stopped by such elaborate nuclear shielding as a sheet of paper.
• Recycled radioactive metal contaminates consumer products | ScrippsNews 25 January 2010 17:43 UTC www.scrippsnews.com [Source type: FILTERED WITH BAYES]

Gamma rays can only be reduced by much more substantial barriers, such as a very thick layer of lead.
.
Different types of decay of a radionuclide.
^ Particular radionuclides decay at different rates, each having its own decay constant ( λ ).

^ Being a radionuclide, the uranium-238 has simply gone through nuclear transformations into different nuclides within the uranium-238 decay chain.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ (For further information about different types of decay, refer to Decay Pathways ) .
• Radioactive Decay Rates - ChemWiki 25 January 2010 17:43 UTC chemwiki.ucdavis.edu [Source type: FILTERED WITH BAYES]

Vertical: atomic number Z, Horizontal: neutron number N
.The dangers of radioactivity and of radiation were not immediately recognized.^ Radiation: The dangers of radioactivity and of radiation were not immediately recognized.
• The Rocky State of Your Campaign #14: Death by Rock, Part Two - RPGnet 25 January 2010 17:43 UTC www.rpg.net [Source type: FILTERED WITH BAYES]

^ User:Bastique/gallery File:Danger radiation.svg File:Radioactivity symbol.png User:C.Thure/Gallery/SVG User:Baleew/Galleries/Icons2 .
• File:Radioactive.svg - Wikimedia Commons 3 February 2010 18:018 UTC commons.wikimedia.org [Source type: Reference]

.Acute effects of radiation were first observed in the use of X-rays when electrical engineer and physicist Nikola Tesla intentionally subjected his fingers to X-rays in 1896. He published his observations concerning the burns that developed, though he attributed them to ozone rather than to X-rays.^ Acute effects of radiation were first observed in the use of X-rays when electric engineer Nikola Tesla intentionally subjected his fingers to X-rays in 1896.
• The Rocky State of Your Campaign #14: Death by Rock, Part Two - RPGnet 25 January 2010 17:43 UTC www.rpg.net [Source type: FILTERED WITH BAYES]

^ He published his observations concerning the burns that developed, though he attributed them to ozone rather than to X-rays.
• The Rocky State of Your Campaign #14: Death by Rock, Part Two - RPGnet 25 January 2010 17:43 UTC www.rpg.net [Source type: FILTERED WITH BAYES]

^ Because radioactive cesium emits ionizing radiation, carcinogenic effects similar to those observed in Japanese survivors of the atomic bombing incidents might be expected among individuals acutely exposed to very high levels of radiation from a radioactive cesium source.
• ATSDR - ToxFAQs™: Cesium 3 February 2010 18:018 UTC www.atsdr.cdc.gov [Source type: Academic]

.His injuries healed later.^ His injuries healed later.
• The Rocky State of Your Campaign #14: Death by Rock, Part Two - RPGnet 25 January 2010 17:43 UTC www.rpg.net [Source type: FILTERED WITH BAYES]

.The genetic effects of radiation, including the effects on cancer risk, were recognized much later.^ The genetic effects of radiation, including the effects on cancer risk, were recognized much later.
• The Rocky State of Your Campaign #14: Death by Rock, Part Two - RPGnet 25 January 2010 17:43 UTC www.rpg.net [Source type: FILTERED WITH BAYES]

^ Evaluation of the risk of potential radiation hazards from fallout involves much the same considerations as do other risks to large populations.
• RADIOACTIVE FALLOUT, 3 February 2010 18:018 UTC www.history.com [Source type: FILTERED WITH BAYES]

^ A value used for estimating the total risk of potential health effects from radiation exposure.
• http://www.pnl.gov/env/appendix_b.html 25 January 2010 17:43 UTC www.pnl.gov [Source type: Academic]

.In 1927 Hermann Joseph Muller published research showing genetic effects, and in 1946 was awarded the Nobel prize for his findings.^ Researchers are often reluctant to report findings too far different from previous results in their published findings.
• RADIOACTIVE AGE ESTIMATION METHODS - Do they prove the earth is billions of years old? - ChristianAnswers.Net 25 January 2010 17:43 UTC christiananswers.net [Source type: Academic]

^ Let's look further at the technique behind the work that led to Libby being awarded a Nobel prize in 1960.
• Radioactive decay and exponential laws 25 January 2010 17:43 UTC plus.maths.org [Source type: Academic]
• Radioactive decay and exponential laws 25 January 2010 17:43 UTC pass.maths.org.uk [Source type: Academic]

.Before the biological effects of radiation were known, many physicians and corporations had begun marketing radioactive substances as patent medicine and radioactive quackery.^ Before the biological effects of radiation were known, many physicians and corporations had begun marketing radioactive substances as patent medicine and radioactive quackery.
• The Rocky State of Your Campaign #14: Death by Rock, Part Two - RPGnet 25 January 2010 17:43 UTC www.rpg.net [Source type: FILTERED WITH BAYES]

^ Once we got past the initial stages of radioactive quackery in which radium and other toxic substances were marketed as medicinal, we successfully implemented radioactivity into a huge variety of processes: medicinal, industrial and domestic.

^ This relationship between the half-life and the decay constant shows that highly radioactive substances are quickly spent, while those that radiate weakly endure longer.

.Examples were radium enema treatments, and radium-containing waters to be drunk as tonics.^ Examples were radium enema treatments, and radium-containing waters to be drunk as tonics.
• The Rocky State of Your Campaign #14: Death by Rock, Part Two - RPGnet 25 January 2010 17:43 UTC www.rpg.net [Source type: FILTERED WITH BAYES]

^ Manufactured from 1918 to 1928 by the Bailey Radium Laboratories, Radithor was a well-known patent tonic that consisted of triple distilled water containing at a least one microcurie of Radium 226 and 228 isotopes.
• 10 Radioactive Products That People Actually Used  | Environmental Graffiti 3 February 2010 18:018 UTC www.environmentalgraffiti.com [Source type: General]

^ Water Treatment Residues million metric tons* *(Note that these categories may contain high-concentration radioactive components.
• MORM - Naturally-Occuring Radioactive Materials Information Page 3 February 2010 18:018 UTC www.ehso.com [Source type: Academic]

.Marie Curie spoke out against this sort of treatment, warning that the effects of radiation on the human body were not well understood (Curie later died from aplastic anemia assumed due to her work with radium, but later examination of her bones showed that she had been a careful laboratory worker and had a low burden of radium.^ Curie later died from aplastic anemia assumed due to her work with radium, but later examination of her bones showed that she had been a careful laboratory worker and had a low burden of radium.
• The Rocky State of Your Campaign #14: Death by Rock, Part Two - RPGnet 25 January 2010 17:43 UTC www.rpg.net [Source type: FILTERED WITH BAYES]

^ Marie Curie spoke out against this sort of treatment, warning that the effects of radiation on the human body were not well understood.
• The Rocky State of Your Campaign #14: Death by Rock, Part Two - RPGnet 25 January 2010 17:43 UTC www.rpg.net [Source type: FILTERED WITH BAYES]

^ Q Eat radiom Radium has similar chemical properties as calcium so if ingested, they take the place of calcium in the bone structure; does this mean that we can intake radium instead of calcium or does radium have other unhealthy side-effects on the human body?
• Questions and Answers on Radioactive Decay 25 January 2010 17:43 UTC www.science.uwaterloo.ca [Source type: FILTERED WITH BAYES]

.A more likely cause was her exposure to unshielded X-ray tubes while a volunteer medical worker in WWI[citation needed]).^ A more likely cause was her exposure to unshielded X-ray tubes while a volunteer medical worker in WWI. .
• The Rocky State of Your Campaign #14: Death by Rock, Part Two - RPGnet 25 January 2010 17:43 UTC www.rpg.net [Source type: FILTERED WITH BAYES]

^ These materials glow in the dark after exposure to light, and he thought that the glow produced in cathode ray tubes by X-rays might somehow be connected with phosphorescence.

^ But a substantial number of these were from causes that had nothing to do with radiation exposure, like accidents, homicide, and suicide.
• Radioactive Baby Teeth Chapter 3 February 2010 18:018 UTC www.radiation.org [Source type: FILTERED WITH BAYES]

.By the 1930s, after a number of cases of bone necrosis and death in enthusiasts, radium-containing medical products had nearly vanished from the market.^ It often contains radium and its decay products.

^ In animal experiments and in human cases of radium poisoning where sufficient amounts of radioactive material are deposited in bone, a higher incidence of LEUKEMIA, (q.v.
• RADIOACTIVE FALLOUT, 3 February 2010 18:018 UTC www.history.com [Source type: FILTERED WITH BAYES]

^ This product, a liquid, came in half-ounce bottles with each bottle guaranteed by the manufacturer to contain 2 Ci of radium.
• Radioactive Quack Cures 3 February 2010 18:018 UTC www.orau.org [Source type: FILTERED WITH BAYES]

## Types of decay

.As for types of radioactive radiation, it was found that an electric or magnetic field could split such emissions into three types of beams.^ The Properties of the three types of Radioactive Emission and symbols .
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ The nature of radioactive emissions Types of radioactivity .
• radioactivity -- Britannica Online Encyclopedia 25 January 2010 17:43 UTC www.britannica.com [Source type: Academic]

^ A type of wave made when an electric field and a magnetic field are combined.
• Dictionary of Cancer Terms - National Cancer Institute 3 February 2010 18:018 UTC www.cancer.gov [Source type: Academic]

.For lack of better terms, the rays were given the alphabetic names alpha, beta and gamma, still in use today.^ The Uses of Radioactive Isotopes emitting alpha, beta and gamma radiation .
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ It is from the nucleus that the radioactivity, the alpha or beta or gamma rays, shoot out.
• Marie Curie - The Unstable Nucleus and its Uses 25 January 2010 17:43 UTC www.aip.org [Source type: FILTERED WITH BAYES]

^ Alpha, beta and gamma rays .
• Chernobyl - Tschernobyl - Information 25 January 2010 17:43 UTC www.chernobyl.info [Source type: Academic]

.While alpha decay was seen only in heavier elements (atomic number 52, tellurium, and greater), the other two types of decay were seen in all of the elements.^ Alpha decay is usually restricted to the heavier elements in the periodic table.

^ Types of radioactivity - Alpha decay .
• radioactivity -- Britannica Online Encyclopedia 25 January 2010 17:43 UTC www.britannica.com [Source type: Academic]

^ Alpha decay -- this type of decay is common for every heavy nuclei.
• Sch001: Nuclear Structure 25 January 2010 17:43 UTC t2.lanl.gov [Source type: FILTERED WITH BAYES]

.In analyzing the nature of the decay products, it was obvious from the direction of electromagnetic forces that alpha rays carried a positive charge, beta rays carried a negative charge, and gamma rays were neutral.^ Natural Alpha Decay: Uranium-238 .
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ The production of beta particles is termed beta decay.

^ Natural Beta Decay: Thorium-234 .
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

.From the magnitude of deflection, it was clear that alpha particles were much more massive than beta particles.^ Being an electron, a beta particle is much smaller and lighter than an alpha particle.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ There are three types of subatomic particles involved: Alpha particles large, easily stopped by paper charge = +2 mass = 4 Beta particles penetrate hundreds of times farther than alpha particles, but easily stopped compared with neutrons and gamma rays.
• Radiometric Dating 25 January 2010 17:43 UTC facstaff.gpc.edu [Source type: Reference]

^ In principle a reaction can involve more than two particles colliding, but because the probability of three or more nuclei to meet at the same time at the same place is much less than for two nuclei, such an event is exceptionally rare.
• What is the difference between radioactive decay, nuclear reactions and nuclear equations? - Yahoo! Answers 25 January 2010 17:43 UTC answers.yahoo.com [Source type: General]

.Passing alpha particles through a very thin glass window and trapping them in a discharge tube allowed researchers to study the emission spectrum of the resulting gas, and ultimately prove that alpha particles are helium nuclei.^ So an alpha particle travels very fast.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ Figure 5: Alpha particle energy spectrum.
• Radiation Notes: Alpha and Beta Decay 25 January 2010 17:43 UTC oak.cats.ohiou.edu [Source type: FILTERED WITH BAYES]

^ "I am very interested to hear the results of the study.
• Radioactive Baby Teeth Chapter 3 February 2010 18:018 UTC www.radiation.org [Source type: FILTERED WITH BAYES]

.Other experiments showed the similarity between beta radiation and cathode rays; they are both streams of electrons, and between gamma radiation and X-rays, which are both high energy electromagnetic radiation.^ Gamma rays are actually high energy photons, the particle analogue of an electromagnetic wave.
• Radioactive Decay | Universe Today 25 January 2010 17:43 UTC www.universetoday.com [Source type: FILTERED WITH BAYES]

^ Gamma rays are electromagnetic radiations such as radio waves, light, and X-rays.
• radioactivity -- Britannica Online Encyclopedia 25 January 2010 17:43 UTC www.britannica.com [Source type: Academic]

^ In other words they both have kinetic energy .
• E = mc^2: Energy from Radioactive Decay 25 January 2010 17:43 UTC www.btinternet.com [Source type: FILTERED WITH BAYES]

.Although alpha, beta, and gamma are most common, other types of decay were eventually discovered.^ The other two are alpha and beta.
• Radioactive Decay | Universe Today 25 January 2010 17:43 UTC www.universetoday.com [Source type: FILTERED WITH BAYES]

^ There are three common types of radioactive decay, alpha, beta, and gamma.
• Radioactive decay and radioactivity 25 January 2010 17:43 UTC physics.bu.edu [Source type: FILTERED WITH BAYES]

^ Alpha decay - - Beta decay .
• radioactivity -- Britannica Online Encyclopedia 25 January 2010 17:43 UTC www.britannica.com [Source type: Academic]

.Shortly after discovery of the neutron in 1932, it was discovered by Enrico Fermi that certain rare decay reactions yield neutrons as a decay particle.^ Encyclopedia II - Radioactive decay - Discovery Radioactivity was first discovered in 1896 by the French scientist Henri Becquerel while working on phosphorescent materials.

^ In it, a neutron decays spontaneously into a proton and an electron, the three natural particles we have in the universe.
• The Relationship between Radioactive Decay and UFOs, Nucelar Bomb, Nuclear Central 25 January 2010 17:43 UTC www.psychovision.ch [Source type: Original source]

^ By around 1932 Rutherford's colleagues had found that the nucleus is built of smaller particles, the positively charged protons and the electrically neutral neutrons.
• Marie Curie - The Unstable Nucleus and its Uses 25 January 2010 17:43 UTC www.aip.org [Source type: FILTERED WITH BAYES]

.Isolated proton emission was eventually observed in some elements.^ With the loss of two protons and two neutrons, the atom has chemically become a different element than what it was before the emission of the alpha particle.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

.Shortly after the discovery of the positron in cosmic ray products, it was realized that the same process that operates in classical beta decay can also produce positrons (positron emission), analogously to negative electrons.^ Also, for example, electron capture, and positron emission (positive beta decay), but not alpha decay, for example.
• xkcd • View topic - Time varying radioactive decay? 25 January 2010 17:43 UTC forums.xkcd.com [Source type: General]

^ A Neutrinos are not product of beta decay, rather particles accompany positron decay.
• Questions and Answers on Radioactive Decay 25 January 2010 17:43 UTC www.science.uwaterloo.ca [Source type: FILTERED WITH BAYES]

^ Beta decay processes are those that involve the release of electrons a.k.a.
• Radioactive Decay | Universe Today 25 January 2010 17:43 UTC www.universetoday.com [Source type: FILTERED WITH BAYES]

.Each of the two types of beta decay acts to move a nucleus toward a ratio of neutrons and protons which has the least energy for the combination.^ When a nucleus decays two things happen .
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

^ Its nucleus contains 6 protons and 8 neutrons.

^ During alpha decay, two neutrons and two protons escape the nucleus as an alpha particle.
• The Age of the Earth - Creationism and Accelerated Decay: Matthew Rognstad 25 January 2010 17:43 UTC orgs.usd.edu [Source type: FILTERED WITH BAYES]

.Finally, in a phenomenon called cluster decay, specific combinations of neutrons and protons other than alpha particles were spontaneously emitted from atoms on occasion.^ During alpha decay, two neutrons and two protons escape the nucleus as an alpha particle.
• The Age of the Earth - Creationism and Accelerated Decay: Matthew Rognstad 25 January 2010 17:43 UTC orgs.usd.edu [Source type: FILTERED WITH BAYES]

^ This two-neutron, two-proton combination — essentially a helium atom minus any electrons — is called an alpha particle.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ The neutron emits an electron to become a proton.
• Radiometric Dating 25 January 2010 17:43 UTC www.tulane.edu [Source type: FILTERED WITH BAYES]

.Still other types of radioactive decay were found which emit previously seen particles, but by different mechanisms.^ Each radioactive nuclide emits radioactivity at its characteristic rate, different from that of other nuclides.
• Physics 30: Atomic Physics - Half-Life and Radioactive Decay 25 January 2010 17:43 UTC www.sasked.gov.sk.ca [Source type: Reference]

^ Radioactive substances emit different types of radiation, which have different ranges.
• Chernobyl - Tschernobyl - Information 25 January 2010 17:43 UTC www.chernobyl.info [Source type: Academic]

^ Types of radioactive decay .
• Types of radioactive decay 25 January 2010 17:43 UTC www.slideshare.net [Source type: Academic]

.An example is internal conversion, which results in electron and sometimes high energy photon emission, even though it involves neither beta nor gamma decay.^ Also, for example, electron capture, and positron emission (positive beta decay), but not alpha decay, for example.
• xkcd • View topic - Time varying radioactive decay? 25 January 2010 17:43 UTC forums.xkcd.com [Source type: General]

^ Beta decay processes are those that involve the release of electrons a.k.a.
• Radioactive Decay | Universe Today 25 January 2010 17:43 UTC www.universetoday.com [Source type: FILTERED WITH BAYES]

^ Internal conversion and electron capture lead to x-ray or Auger electron emission.
• Radioactive Transitions 3 February 2010 18:018 UTC www.sprawls.org [Source type: FILTERED WITH BAYES]

## Decay modes in table form

.Radionuclides can undergo a number of different reactions.^ Radionuclides can undergo a number of different reactions.

^ Transmutation describes a process by which the nucleus of a radioactive atom undergoes decay into an atom with a different number of protons, until such time as a stable nucleus is produced.
• Physics 30: Atomic Physics - Half-Life and Radioactive Decay 25 January 2010 17:43 UTC www.sasked.gov.sk.ca [Source type: Reference]

^ When an unstable nucleus splits a different nucleus with a different number of protons is formed and so a different element is formed (NOT possible in chemical changes, but this is a nuclear reaction!
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

.These are summarized in the following table.^ These are summarized in the following table, in rough order of increasing rarity.

^ The characteristics of each of these are given within the following table: Not available at this time TABLE H.1 Radioactive Sources and Emission Types MEASUREMENT OF DOSE .
• Appendix H: Radioactive tracers 3 February 2010 18:018 UTC homepages.gac.edu [Source type: FILTERED WITH BAYES]

.A nucleus with mass number A and atomic number Z is represented as (A, Z).^ An atom is characterized by its mass number (A) and its atomic number (Z).
• Isotopes for Medicine and the Life Sciences 25 January 2010 17:43 UTC www.nap.edu [Source type: Academic]

^ Neutron number (N) The number of neutrons in an atomic nucleus.
• Isotopes for Medicine and the Life Sciences 25 January 2010 17:43 UTC www.nap.edu [Source type: Academic]

^ Synonym: atomic mass number .

.The column "Daughter nucleus" indicates the difference between the new nucleus and the original nucleus.^ The original nucleus is designated the parent, and the nucleus after the transition is designated the daughter.
• Radioactive Transitions 3 February 2010 18:018 UTC www.sprawls.org [Source type: FILTERED WITH BAYES]

^ If the mass of a helium nucleus is examined, there is a difference between the expected mass based on its proton and neutron composition, and the actual measured mass.
• Appendix H: Radioactive tracers 3 February 2010 18:018 UTC homepages.gac.edu [Source type: FILTERED WITH BAYES]

^ These gamma-ray transitions may be from a metastable excited state, or between levels in a daughter nucleus.
• NIST: Ionizing Radiat. Div. - Glossary of Terms 25 January 2010 17:43 UTC physics.nist.gov [Source type: Academic]

.Thus, (A–1, Z) means that the mass number is one less than before, but the atomic number is the same as before.^ Synonym: atomic mass number .

^ An atom is characterized by its mass number (A) and its atomic number (Z).
• Isotopes for Medicine and the Life Sciences 25 January 2010 17:43 UTC www.nap.edu [Source type: Academic]

^ Gamma emission : The emission of gamma radiation from a nucleus does not involve any change in the atomic (proton) number or mass number.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

Mode of decay Participating particles Daughter nucleus
Decays with emission of nucleons:
Alpha decay An alpha particle (A=4, Z=2) emitted from nucleus (A–4, Z–2)
Proton emission A proton ejected from nucleus (A–1, Z–1)
Neutron emission A neutron ejected from nucleus (A–1, Z)
Double proton emission Two protons ejected from nucleus simultaneously (A–2, Z–2)
Spontaneous fission Nucleus disintegrates into two or more smaller nuclei and other particles -
Cluster decay Nucleus emits a specific type of smaller nucleus (A1, Z1) smaller than, or larger than, an alpha particle (AA1, ZZ1) + (A1,Z1)
Different modes of beta decay:
Beta-Negative decay A nucleus emits an electron and an antineutrino (A, Z+1)
Positron emission, also Beta-Positive decay A nucleus emits a positron and a neutrino (A, Z–1)
Electron capture A nucleus captures an orbiting electron and emits a neutrino — The daughter nucleus is left in an excited and unstable state (A, Z–1)
Double beta decay A nucleus emits two electrons and two antineutrinos (A, Z+2)
Double electron capture A nucleus absorbs two orbital electrons and emits two neutrinos — The daughter nucleus is left in an excited and unstable state (A, Z–2)
Electron capture with positron emission A nucleus absorbs one orbital electron, emits one positron and two neutrinos (A, Z–2)
Double positron emission A nucleus emits two positrons and two neutrinos (A, Z–2)
Transitions between states of the same nucleus:
Isomeric transition Excited nucleus releases a high-energy photon (gamma ray) (A, Z)
Internal conversion Excited nucleus transfers energy to an orbital electron and it is ejected from the atom (A, Z)
.Radioactive decay results in a reduction of summed rest mass, once the released energy (the disintegration energy) has escaped.^ Radioactive decay results in a loss of mass, which is converted to energy (the disintegration energy) according to the formula E = mc2.

^ Radioactive decay is described in terms of the probability that a constituent particle of the nucleus of an atom will escape through the potential (Energy) barrier which bonds them to the nucleus.
• Radiometric Dating 25 January 2010 17:43 UTC www.tulane.edu [Source type: FILTERED WITH BAYES]

^ When a muon decays, the reduction in rest mass present will be compensated by an increase in kinetic energy, in order that the total mass-energy stay constant.
• Radiation Notes: Alpha and Beta Decay 25 January 2010 17:43 UTC oak.cats.ohiou.edu [Source type: FILTERED WITH BAYES]

.The energy carries mass with it (see mass in special relativity) according to the formula E = mc2.^ The total masses of the positron and the electron are converted into energy according to the relationship .
• Radioactive Transitions 3 February 2010 18:018 UTC www.sprawls.org [Source type: FILTERED WITH BAYES]

^ At such high energy levels, the matter can be converted directly to energy according to Einstein's famous Mass-Energy relationship E = mc 2 .

^ The species is often represented by a formula with a single dot as the unpaired electron (see immediately below).
• Atmospheric Chemistry Glossary 25 January 2010 17:43 UTC www.shsu.edu [Source type: Academic]

.The decay energy is initially released as kinetic energy of the emitted particles.^ Calculate the maximum kinetic energy of the positron emitted in the decay 8 5 B ?

^ Radioactive decay is described in terms of the probability that a constituent particle of the nucleus of an atom will escape through the potential (Energy) barrier which bonds them to the nucleus.
• Radiometric Dating 25 January 2010 17:43 UTC www.tulane.edu [Source type: FILTERED WITH BAYES]

^ Emitted energy from the decay of radium ionizes gases, affects photographic plates, causes sores on the skin, and produces many other detrimental effects.
• The Rocky State of Your Campaign #14: Death by Rock, Part Two - RPGnet 25 January 2010 17:43 UTC www.rpg.net [Source type: FILTERED WITH BAYES]

Later these particles come to thermal equilibrium with their surroundings. .The energy remains associated with a measure of mass of the decay system invariant mass, in as much as the kinetic energy of emitted particles, and, later, the thermal energy of the surrounding matter, contributes also to the total invariant mass of systems.^ As the tritium decays, it emits Beta particles (high energy electrons).

^ Calculate the maximum kinetic energy of the positron emitted in the decay 8 5 B ?

^ The equation above can be reached easily from any beta decay reaction, however, it is not useful because mass spectrometers measure the mass of atoms rather than just their nuclei.

.Thus, the sum of rest masses of particles is not conserved in decay, but the system mass or system invariant mass (as also system total energy) is conserved.^ The sum of mass and energy are conserved in nuclear decay.

^ A neutrino is a zero-rest mass spin 1/2 particle which conserves momentum in the decay process.

^ Beta particle - β− decay electron Beta particle - β+ decay positron Beta particle - The neutrino and conservation of energy .

## Decay chains and multiple modes

.The daughter nuclide of a decay event may also be unstable (radioactive).^ The nuclide produced in radioactive decay.

^ An nuclide capable of undergoing radioactive decay.

^ A parent decays to a daughter nuclide.

.In this case, it will also decay, producing radiation.^ Ionization is a particular characteristic of the radiation produced when radioactive elements decay.

^ In the case of tropospheric fallout, some radioactive decay occurs in the atmosphere, thereby reducing somewhat the radiation dosage to those exposed on the earth's surface.
• RADIOACTIVE FALLOUT, 3 February 2010 18:018 UTC www.history.com [Source type: FILTERED WITH BAYES]

.The resulting second daughter nuclide may also be radioactive.^ The relationship of a nuclide to a second nuclide through a single radioactive decay.

^ The nuclides fed in the radioactive decay of 238 U including all daughters through stable 206 Pb.

^ However, it is with the interpretation of the chemical analyses of the radioactive parents and resultant daughters that the problems with radioactive dating of rocks begin.
• Radioactive dating method ‘under fire’ 3 February 2010 18:018 UTC www.answersingenesis.org [Source type: FILTERED WITH BAYES]

This can lead to a sequence of several decay events. .Eventually a stable nuclide is produced.^ In the previous section we showed that certain nuclei are not completely stable and eventually undergo an internal change that will produce a more stable nuclear structure.
• Radioactive Transitions 3 February 2010 18:018 UTC www.sprawls.org [Source type: FILTERED WITH BAYES]

.This is called a decay chain.^ This process of turning into stable nuclides through a series of decays is called the radioactive decay series or decay chain.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

.
Gamma-ray energy spectrum of 238U (inset).
^ Because gamma radiation loses energy slowly, gamma rays are able to travel significant distances.  Depending upon their initial energy, gamma rays can travel tens or hundreds of meters in air.

^ The use of high-energy radiation from x-rays, gamma rays, neutrons, protons, and other sources to kill cancer cells and shrink tumors.
• Dictionary of Cancer Terms - National Cancer Institute 3 February 2010 18:018 UTC www.cancer.gov [Source type: Academic]

^ Gamma rays are emitted when a nucleus changes from a higher to a lower energy state; with most radionuclides, this gamma emission accompanies alpha or beta decay.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

.Gamma-rays are emitted by decaying nuclides, and the gamma-ray energy can be used to characterize the decay (which nuclide is decaying to which).^ Gamma radiation: High-energy, short wavelength, electromagnetic radiation emitted from the nucleus of radioacitve elements.
• Chernobyl - Tschernobyl - Information 25 January 2010 17:43 UTC www.chernobyl.info [Source type: Academic]

^ Emitted energy from the decay of radium ionizes gases, affects photographic plates, causes sores on the skin, and produces many other detrimental effects.
• The Rocky State of Your Campaign #14: Death by Rock, Part Two - RPGnet 25 January 2010 17:43 UTC www.rpg.net [Source type: FILTERED WITH BAYES]

^ Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power * GCSE-AS Radioactivity , properties & uses of alpha/beta/gamma radiation , radioisotopes, nuclear reactions .
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

Here, using the gamma-ray spectrum, several nuclides which are typical of the decay chain have been identified: 226Ra, 214Pb, 214Bi.
An example is the natural decay chain of 238U which is as follows:
• decays, through alpha-emission, with a half-life of 4.5 billion years to thorium-234
• which decays, through beta-emission, with a half-life of 24 days to protactinium-234
• which decays, through beta-emission, with a half-life of 1.2 minutes to uranium-234
• which decays, through alpha-emission, with a half-life of 240 thousand years to thorium-230
• which decays, through alpha-emission, with a half-life of 77 thousand years to radium-226
• which decays, through alpha-emission, with a half-life of 1.6 thousand years to radon-222
• which decays, through alpha-emission, with a half-life of 3.8 days to polonium-218
• which decays, through alpha-emission, with a half-life of 3.1 minutes to lead-214
• which decays, through beta-emission, with a half-life of 27 minutes to bismuth-214
• which decays, through beta-emission, with a half-life of 20 minutes to polonium-214
• which decays, through alpha-emission, with a half-life of 160 microseconds to lead-210
• which decays, through beta-emission, with a half-life of 22 years to bismuth-210
• which decays, through beta-emission, with a half-life of 5 days to polonium-210
• which decays, through alpha-emission, with a half-life of 140 days to lead-206, which is a stable nuclide.
.Some radionuclides may have several different paths of decay.^ Some nuclides like 232 Th have several members of its decay chain.
• Natural Radioactivity 3 February 2010 18:018 UTC physics.isu.edu [Source type: Academic]

^ Being a radionuclide, the uranium-238 has simply gone through nuclear transformations into different nuclides within the uranium-238 decay chain.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ Encyclopedia II - Radioactive decay - Modes of decay Radionuclides can undergo a number of different reactions.

.For example, approximately 36% of bismuth-212 decays, through alpha-emission, to thallium-208 while approximately 64% of bismuth-212 decays, through beta-emission, to polonium-212.^ Alpha decay - - Beta decay .
• radioactivity -- Britannica Online Encyclopedia 25 January 2010 17:43 UTC www.britannica.com [Source type: Academic]

^ Alpha decay - Beta-minus decay .
• radioactivity -- Britannica Online Encyclopedia 25 January 2010 17:43 UTC www.britannica.com [Source type: Academic]

^ Carbon-14, like the potassium-argon and rubidium-strontium isotope dating methods RATE indicts, is an example of beta decay.
• The Age of the Earth - Creationism and Accelerated Decay: Matthew Rognstad 25 January 2010 17:43 UTC orgs.usd.edu [Source type: FILTERED WITH BAYES]

.Both the thallium-208 and the polonium-212 are radioactive daughter products of bismuth-212, and both decay directly to stable lead-208.^ Decay in radioactivity of fission products .
• Nuclear waste management - Encyclopedia of Earth 3 February 2010 18:018 UTC www.eoearth.org [Source type: FILTERED WITH BAYES]

^ The daughter product may be stable or it may decay to form a daughter product of its own.

^ At the same time, it is also important to distinguish between the naturally occurring radioactive decay products like radium-226, radon-222, and polonium-210 and those radioactive “fission products” produced by the fissioning (or splitting) of uranium isotopes in a nuclear reaction.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

## Occurrence and applications

.According to the Big Bang theory, stable isotopes of the lightest five elements (H, He, and traces of Li, Be, and B) were produced very shortly after the emergence of the universe, in a process called Big Bang nucleosynthesis.^ This tends to happen with isotopes with too many neutrons to be stable (too high an n/p ratio) and lies above the stability curve shown in a previous graph.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ Usually, we know the amount, N, of an isotope present today, and the amount of a daughter element produced by decay, D*.
• Radiometric Dating 25 January 2010 17:43 UTC www.tulane.edu [Source type: FILTERED WITH BAYES]

^ This process of becoming stable over time is called radioactive decay — because the radioactivity of the radionuclide is actually decaying away, or declining, over time.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

.These lightest stable nuclides (including deuterium) survive to today, but any radioactive isotopes of the light elements produced in the Big Bang (such as tritium) have long since decayed.^ The more radioactive an isotope is, the faster it decays.
• Nuclear waste management - Encyclopedia of Earth 3 February 2010 18:018 UTC www.eoearth.org [Source type: FILTERED WITH BAYES]

^ Usually, we know the amount, N, of an isotope present today, and the amount of a daughter element produced by decay, D*.
• Radiometric Dating 25 January 2010 17:43 UTC www.tulane.edu [Source type: FILTERED WITH BAYES]

^ Several elements have both a stable and one or more radioactive isotopes.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

.Isotopes of elements heavier than boron were not produced at all in the Big Bang, and these first five elements do not have any long-lived radioisotopes.^ Long lived isotopes of uranium (element 92) decay via a complicated series of relatively short-lived radioisotopes to produce stable isotopes of lead (element 82).
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ Atomic nucleus - Nuclear Makeup Atomic nucleus - Isotopes Atomic nucleus - Nuclear Decay Atomic nucleus - Nucleus Size Atomic nucleus - History Atomic nucleus - Nuclear Fusion Atomic nucleus - Nuclear Fission Atomic nucleus - Production of Heavy Elements Atomic nucleus - Nuclear Physics .

^ For any element with an atomic number greater than 83 (bismuth), all isotopes are radioactive.
• Open Course : Astronomy : Introduction : Lecture 7 : Nature of Matter 25 January 2010 17:43 UTC www.opencourse.info [Source type: FILTERED WITH BAYES]

.Thus, all radioactive nuclei are therefore relatively young with respect to the birth of the universe, having formed later in various other types of nucleosynthesis in stars (particularly supernovae), and also during ongoing interactions between stable isotopes and energetic particles.^ The probability that particles will disintegrate in the time interval is given by ], where is the initial number of nuclei present and is the decay constant characteristic of the radioactive isotope.
• Radioactive Decay as a Probability Distribution - Wolfram Demonstrations Project 25 January 2010 17:43 UTC demonstrations.wolfram.com [Source type: FILTERED WITH BAYES]

^ Some types (technically known as ‘isotopes’) of ‘parent’ elements such as uranium, thorium, potassium and rubidium are said to be radioactive because the nuclei of the atoms are unstable, resulting in readjustments between the ‘particles’ (primarily neutrons and protons) in the nuclei with time.
• Radioactive dating method ‘under fire’ 3 February 2010 18:018 UTC www.answersingenesis.org [Source type: FILTERED WITH BAYES]

^ The nuclides fed in the radioactive decay of 238 U including all daughters through stable 206 Pb.

.For example, carbon-14, a radioactive nuclide with a half-life of only 5730 years, is constantly produced in Earth's upper atmosphere due to interactions between cosmic rays and nitrogen.^ A very small % of them are radioactive due to carbon-14 with a half-life of 5700 years.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ Yep, 4.5 billion year half-life.
• Recycled radioactive metal contaminates consumer products | ScrippsNews 25 January 2010 17:43 UTC www.scrippsnews.com [Source type: FILTERED WITH BAYES]

^ Carbon-14 is constantly created and constantly decays .
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

.Radioactive decay has been put to use in the technique of radioisotopic labeling, which is used to track the passage of a chemical substance through a complex system (such as a living organism).^ Encyclopedia - Artificial disintegration Artificial disintegration is the term coined by Ernest Rutherford for the process by which an atomic nucleus is broken down by bombarding it with high speed alpha particles, either from a particle accelerator, or a naturally decaying radioactive substance such as radium, as Rutherford originally used.

^ Radioactive decay is described in terms of the probability that a constituent particle of the nucleus of an atom will escape through the potential (Energy) barrier which bonds them to the nucleus.
• Radiometric Dating 25 January 2010 17:43 UTC www.tulane.edu [Source type: FILTERED WITH BAYES]

^ The value of the biological half-life is determined by such things as the chemical form of the radionuclide and the physiological function of the organ or organism considered.
• Radioactivity 25 January 2010 17:43 UTC www.sprawls.org [Source type: Academic]

.A sample of the substance is synthesized with a high concentration of unstable atoms.^ The radioactivity of any sample will decrease with time as the unstable atoms decay to more stable atoms, though sometimes by complex decay series routes e.g.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ This means that it’s not possible to know which particular atom in a sample of a radioactive substance will decay and when.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

.The presence of the substance in one or another part of the system is determined by detecting the locations of decay events.^ As is usual in beta decay, that part of the energy carried away by the neutrinos is not detected, but the kinetic energy of the decay electron (or positron) can be.
• Radiation Notes: Alpha and Beta Decay 25 January 2010 17:43 UTC oak.cats.ohiou.edu [Source type: FILTERED WITH BAYES]

^ A measure of the odds of an event happening in one group compared to the odds of the same event happening in another group.
• Dictionary of Cancer Terms - National Cancer Institute 3 February 2010 18:018 UTC www.cancer.gov [Source type: Academic]

^ A type of systemic radiation therapy in which a radioactive substance is linked to an antibody that locates and kills tumor cells when injected into the body.
• Dictionary of Cancer Terms - National Cancer Institute 3 February 2010 18:018 UTC www.cancer.gov [Source type: Academic]

.On the premise that radioactive decay is truly random (rather than merely chaotic), it has been used in hardware random-number generators.^ Radioactive decay and the myth of randomness Options .
• Radioactive decay and the myth of randomness - sci.logic | Google Groups 25 January 2010 17:43 UTC groups.google.com [Source type: FILTERED WITH BAYES]

^ The equation above can be reached easily from any beta decay reaction, however, it is not useful because mass spectrometers measure the mass of atoms rather than just their nuclei.

^ The probability that particles will disintegrate in the time interval is given by ], where is the initial number of nuclei present and is the decay constant characteristic of the radioactive isotope.
• Radioactive Decay as a Probability Distribution - Wolfram Demonstrations Project 25 January 2010 17:43 UTC demonstrations.wolfram.com [Source type: FILTERED WITH BAYES]

.Because the process is not thought to vary significantly in mechanism over time, it is also a valuable tool in estimating the absolute ages of certain materials.^ This process of becoming stable over time is called radioactive decay — because the radioactivity of the radionuclide is actually decaying away, or declining, over time.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ There is often a diurnal (over a day) variation in the process of smog formation because one of the necessary components for its formation is sunlight.
• Atmospheric Chemistry Glossary 25 January 2010 17:43 UTC www.shsu.edu [Source type: Academic]

^ Radiocarbon Dating - Establishing the relative age of various materials with the use of carbon-14.
• Atmospheric Chemistry Glossary 25 January 2010 17:43 UTC www.shsu.edu [Source type: Academic]

.For geological materials, the radioisotopes and some of their decay products become trapped when a rock solidifies, and can then later be used (subject to many well-known qualifications) to estimate the date of the solidification.^ Some examples of isotope systems used to date geologic materials.
• Radiometric Dating 25 January 2010 17:43 UTC www.tulane.edu [Source type: FILTERED WITH BAYES]

^ Understanding half-lives is also an important key to dating many different materials, e.g., organic materials that are as much as 50,000 years old (see Lesson 3 of this unit, especially the student activity entitled “Using Radionuclides to Date Materials”).
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ By other means, the oldest age estimate, to date, for an Earth rock is 3.96 billion years (Slave Province, Canada).
• RADIOACTIVE AGE ESTIMATION METHODS - Do they prove the earth is billions of years old? - ChristianAnswers.Net 25 January 2010 17:43 UTC christiananswers.net [Source type: Academic]

.These include checking the results of several simultaneous processes and their products against each other, within the same sample.^ These include persistent effects of chemical states and physical environment and the natural, low-energy transmutation phenomena associated with the vegetation processes of plants.

^ If these multiple isotopic analyses of various rock samples, and minerals within those rock samples, are from the same geological unit, then geochronologists can also use what is known as the isochron age determination method.
• Radioactive dating method ‘under fire’ 3 February 2010 18:018 UTC www.answersingenesis.org [Source type: FILTERED WITH BAYES]

^ Physicist Donald DeYoung , Ph.D.: "The different methods of radiometric dating, when checked against each other, often are in approximate agreement.
• RADIOACTIVE AGE ESTIMATION METHODS - Do they prove the earth is billions of years old? - ChristianAnswers.Net 25 January 2010 17:43 UTC christiananswers.net [Source type: Academic]

.In a similar fashion, and also subject to qualification, the rate of formation of carbon-14 in various eras, the date of formation of organic matter within a certain period related to the isotope's half-live may be estimated, because the carbon-14 becomes trapped when the organic matter grows and incorporates the new carbon-14 from the air.^ Archaeological dating with the isotope carbon -14 .
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ After n half-lives the activity will be some fraction, f, of the rate of formation or saturation activity.
• Radioactivity 25 January 2010 17:43 UTC www.sprawls.org [Source type: Academic]

^ Qaim et al "Half-Lives and Activation Cross-Sections of Some Radio-Isotopes of Iodine, Tellurium and Anatimon Formed in the Interaction of Iodine with 14.7 MeV Neurons"--see the whole document.
• Method and apparatus for production of radioactive iodine - Patent 6056929 25 January 2010 17:43 UTC www.freepatentsonline.com [Source type: Academic]

.Thereafter, the amount of carbon-14 in organic matter decreases according to decay processes which may also be independently cross-checked by other means (such as checking the carbon-14 in individual tree rings, for example).^ Carbon-14 is constantly created and constantly decays .
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

^ This means the carbon-14 % remains constant.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ The radioactivity of the carbon-14 begins to decrease.
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

## Radioactive decay rates

The decay rate, or activity, of a radioactive substance are characterized by:
Constant quantities:
• half life — symbol t1/2 — the time taken for the activity of a given amount of a radioactive substance to decay to half of its initial value.
• mean lifetime — symbol τ — the average lifetime of a radioactive particle.
• decay constant — symbol λ — the inverse of the mean lifetime.
.Although these are constants, they are associated with statistically random behavior of populations of atoms.^ The outcome is no longer random, because these groups of possible worlds all have single outcomes (the atom decays at the same time in each possible world -- /within each subgroup/, that is).
• Radioactive decay and the myth of randomness - sci.logic | Google Groups 25 January 2010 17:43 UTC groups.google.com [Source type: FILTERED WITH BAYES]

^ These are called “fast neutrons.” They are very penetrating of substances, but they do not get involved in nuclear reactions within individual atoms.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ The outcome is no longer random, because > these groups of possible worlds all have single outcomes > (the atom decays at the same time in each possible > world -- /within each subgroup/, that is).
• Radioactive decay and the myth of randomness - sci.logic | Google Groups 25 January 2010 17:43 UTC groups.google.com [Source type: FILTERED WITH BAYES]

.In consequence predictions using these constants are less accurate for small number of atoms.^ Other minerals that also show these properties, but are less commonly used in radiometric dating are Apatite and sphene.
• Radiometric Dating 25 January 2010 17:43 UTC www.tulane.edu [Source type: FILTERED WITH BAYES]

^ One consequence of fission is that more neutrons are formed, these in turn 'split' other atoms making even more neutrons .
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ The rate of radioactive decay is therefore the product of a rate constant ( k ) times the number of atoms of the isotope in the sample ( N ).

Time-variable quantities:
.
• Total activity — symbol A — number of decays an object undergoes per second.
• Number of particles — symbol N — the total number of particles in the sample.
• Specific activity — symbol SA — number of decays per second per amount of substance.^ We now consider the relationship of activity and the number of nuclei, N, in a specific sample.
• Radioactivity 25 January 2010 17:43 UTC www.sprawls.org [Source type: Academic]

^ Therefore, given a sample of a particular radioisotope, the number of decay events –dN expected to occur in a small interval of time dt is proportional to the number of atoms present.

^ The standard definition of half-life or half-decay time is the time taken by a given amount of a particular radioactive substance to undergo disintegration or decay of half of its atoms.  Measured half-lives vary from less than a millionth of a second to billions of years in the case of Uranium.

.(The "amount of substance" can be the unit of either mass or volume.^ The amount of a radioactive substance is measured not only in measure units (gram, milligram, etc.
• Chernobyl - Tschernobyl - Information 25 January 2010 17:43 UTC www.chernobyl.info [Source type: Academic]

^ Relation of the radionuclide activity in a substance to the substance mass (volume).
• Chernobyl - Tschernobyl - Information 25 January 2010 17:43 UTC www.chernobyl.info [Source type: Academic]

^ The wavelength of light scattered is dependent on the D p , and the amount of light scattered is dependent on the number of particles present per unit volume.
• Atmospheric Chemistry Glossary 25 January 2010 17:43 UTC www.shsu.edu [Source type: Academic]

)
These are related as follows:
$t_{1/2} = \frac{\ln(2)}{\lambda} = au \ln(2)$
$A = - \frac{dN}{dt} = \lambda N$
$S_A a_0 = - \frac{dN}{dt}\bigg|_{t=0} = \lambda N_0$
where .a0 is the initial amount of active substance — substance that has the same percentage of unstable particles as when the substance was formed.^ Since the total momentum is initially zero, the alpha particle and the daughter nuclues must move in exactly opposite directions with the same magnitude of momentum.
• Radiation Notes: Alpha and Beta Decay 25 January 2010 17:43 UTC oak.cats.ohiou.edu [Source type: FILTERED WITH BAYES]

### Activity measurements

.The units in which activities are measured are: becquerel (symbol Bq) = number of disintegrations per second; curie (Ci) = 3.7 × 1010 disintegrations per second.^ (Bq) means 1 count per second .
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

^ Two units are used: the becquerel (Bq), equivalent to 1 tps, and the curie (Ci), equivalent to 3.7 x 10 10 tps.
• Radioactivity 25 January 2010 17:43 UTC www.sprawls.org [Source type: Academic]

^ B ecquerel units (Bq, s -1 ) , 1 becquerel = 1 disintegration of an unstable nucleus per second.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

.Low activities are also measured in disintegrations per minute (dpm).^ The natural abundance of 14 C is about 1 part in 10 12 and the average activity of living tissue is 15.3 disintegrations per minute per gram of carbon.

^ The curie is now defined as the amount of radioactive isotope necessary to achieve an activity of 3.700 x 10 10 disintegrations per second.

^ Activity measure unit in the Si (Si - the International System of Units, the most widely used system of units) is the decay per second (decay/sec).
• Chernobyl - Tschernobyl - Information 25 January 2010 17:43 UTC www.chernobyl.info [Source type: Academic]

## Decay timing

.The decay of an unstable nucleus is entirely random and it is impossible to predict when a particular atom will decay.^ The decay of a given nucleus is completely random .
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

^ But the decay of a given nucleus is completely random.
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

^ Radioactivity results from the random and spontaneous breakdown of the unstable nucleus of an atom.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

[1] .However, it is equally likely to decay at any time.^ However, it is equally likely to decay at any time.

^ Exponential decay means that equal periods of time give equal proportional changes in radioactivity.
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

^ If, however, the isotope is only a little way up from the bottom of the valley, alpha decay may be about as likely as beta decay.
• Radiation Notes: Alpha and Beta Decay 25 January 2010 17:43 UTC oak.cats.ohiou.edu [Source type: FILTERED WITH BAYES]

.Therefore, given a sample of a particular radioisotope, the number of decay events −dN expected to occur in a small interval of time dt is proportional to the number of atoms present.^ Therefore, given a sample of a particular radioisotope, the number of decay events –dN expected to occur in a small interval of time dt is proportional to the number of atoms present.

^ The rate of radioactive decay is therefore the product of a rate constant ( k ) times the number of atoms of the isotope in the sample ( N ).

^ The standard definition of half-life or half-decay time is the time taken by a given amount of a particular radioactive substance to undergo disintegration or decay of half of its atoms.  Measured half-lives vary from less than a millionth of a second to billions of years in the case of Uranium.

If N is the number of atoms, then the probability of decay (−dN/N) is proportional to dt:
$\left(-\frac{dN}{N} \right) = \lambda \cdot dt.$
.Particular radionuclides decay at different rates, each having its own decay constant (λ).^ Methodological errors could exist in any of these phenomena, but taken together the evidence of constant decay rates is compelling (Stassen 2005).
• The Age of the Earth - Creationism and Accelerated Decay: Matthew Rognstad 25 January 2010 17:43 UTC orgs.usd.edu [Source type: FILTERED WITH BAYES]

^ There has been in recent years the horrible realization that radio-decay rates are not as constant as previously thought, nor are they immune to environmental influences.
• RADIOACTIVE AGE ESTIMATION METHODS - Do they prove the earth is billions of years old? - ChristianAnswers.Net 25 January 2010 17:43 UTC christiananswers.net [Source type: Academic]

^ This leads them to discount all three assumptions that underlie radioisotope decay: knowable initial condition, closed system, and constant decay rate (Vardiman et al.
• The Age of the Earth - Creationism and Accelerated Decay: Matthew Rognstad 25 January 2010 17:43 UTC orgs.usd.edu [Source type: FILTERED WITH BAYES]

The negative sign indicates that N decreases with each decay event. The solution to this first-order differential equation is the following function:
$N(t) = N_0\,e^{-{\lambda}t} = N_0\,e^{-t/ au}. \,\!$
Where N0 is the value of N at time zero (t = 0). .The second equation recognizes that the differential decay constant λ has units of 1/time, and can thus also be represented as 1/τ, where τ is a characteristic time for the process.^ This process of becoming stable over time is called radioactive decay — because the radioactivity of the radionuclide is actually decaying away, or declining, over time.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ The shorter the half-life of the radionuclide, the more atoms of this radionuclide will decay per unit time for a given mass of radionuclide.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ During the decay process, the chemical environment of the nucleus is changed, thus altering the decay constant.

.This characteristic time is called the time constant of the process.^ This process of becoming stable over time is called radioactive decay — because the radioactivity of the radionuclide is actually decaying away, or declining, over time.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

.In radioactive decay, this process time constant is also the mean lifetime for decaying atoms.^ But it will not give a guarantee of the time the atom will decay.
• Radioactive decay and the myth of randomness - sci.logic | Google Groups 25 January 2010 17:43 UTC groups.google.com [Source type: FILTERED WITH BAYES]

^ Definition and meaning of radioactive decay : .

^ Therefore, given a sample of a particular radioisotope, the number of decay events –dN expected to occur in a small interval of time dt is proportional to the number of atoms present.

Each atom "lives" for a finite amount of time before it decays, and it may be shown that this mean lifetime is the arithmetic mean of all the atoms' lifetimes, and that it is τ, which again is related to the decay constant as follows:
$au = \frac{1}{\lambda}.$
.
Simulation of many identical atoms undergoing radioactive decay, starting with either 4 atoms (left) or 400 (right).
^ An nuclide capable of undergoing radioactive decay.

^ Most atoms with an atomic number of over 82 (Pb) usually undergo alpha decay.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ Any radioactive decay series goes on until the atom becomes stable, or non-radioactive.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

.The number at the top indicates how many half-lives have elapsed.^ How many more destroyed lives will it take?
• Cancer – The Deadly Legacy of the Invasion of Iraq | CommonDreams.org 25 January 2010 17:43 UTC www.commondreams.org [Source type: General]

^ Many even have longer half-lives, such as the persistent hormone-like POP's that casue harm in absolutely tiny amounts.
• Cancer – The Deadly Legacy of the Invasion of Iraq | CommonDreams.org 25 January 2010 17:43 UTC www.commondreams.org [Source type: General]

^ In the next lesson we’ll extend these ideas so we can work out what happens when we’re not dealing with a whole number of half-lives.
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

Note the law of large numbers: With more atoms, the overall decay is less random.
The previous exponential function generally represents the result of exponential decay. It is only an approximate solution, for two reasons. .Firstly, the exponential function is continuous, but the physical quantity N can only take non-negative integer values.^ Z denotes either a positive, negative or zero integer, the j Z are complex functions of x m , j Z and j Z are complex conjugates, and j 0 is real.
• A Mechanism for Accelerated Radioactive Decay 25 January 2010 17:43 UTC www.creationresearch.org [Source type: Academic]

^ Theories which have variation while keeping all dimensionless ratios constant are physically trivial, amounting only to a continual redefinition of units over time.
• A Mechanism for Accelerated Radioactive Decay 25 January 2010 17:43 UTC www.creationresearch.org [Source type: Academic]

^ A mob of people (corporation) whose only collective commonality is greed will continue to rape and pillage until the society around them is non-functioning, like a cancer.
• The BRAD BLOG : Activist U.S. Supreme Court Makes It Official, We're Now 'The Corporate States of America' 25 January 2010 17:43 UTC www.bradblog.com [Source type: General]

.Secondly, because it describes a random process, it is only statistically true.^ The radioactive decay process is both random and statistically predictable.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

However, in most common cases, N is an extremely large number (comparable to Avogadro's number) and the function is a good approximation.

### Half life

.A more commonly used parameter is the half-life.^ Using half-life in simple calculations .
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

^ Technium-99 is a gamma emitter (half-life 6 hours) and is used as a medical tracer .
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ The shorter the half-life of the radionuclide, the more atoms of this radionuclide will decay per unit time for a given mass of radionuclide.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

.Given a sample of a particular radionuclide, the half-life is the time taken for half the radionuclide's atoms to decay.^ The shorter the half-life of the radionuclide, the more atoms of this radionuclide will decay per unit time for a given mass of radionuclide.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ Put another way, the half-life of a radionuclide is the time for one-half of any given quantity of that radionuclide to decay.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ But it will not give a guarantee of the time the atom will decay.
• Radioactive decay and the myth of randomness - sci.logic | Google Groups 25 January 2010 17:43 UTC groups.google.com [Source type: FILTERED WITH BAYES]

The half life is related to the decay constant as follows:
$t_{1/2} = \frac{\ln 2}{\lambda} = au \ln 2.$
.This relationship between the half-life and the decay constant shows that highly radioactive substances are quickly spent, while those that radiate weakly endure longer.^ Drag the shaded area to show that the half-life stays constant.
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

^ The radioactivity halves with each half-life.
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

^ Now let’s try and explain why radioactive decay has a CONSTANT ‘half-life’.
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

.Half-lives of known radionuclides vary widely, from more than 1019 years (such as for very nearly stable nuclides, e.g.^ Radionuclides that exist for more than 30 half-lives are not measurable.
• Natural Radioactivity 3 February 2010 18:018 UTC physics.isu.edu [Source type: Academic]

^ Each half-life is 10 years.
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

^ In this case the half-life is 10 years.
• Half-life simulation, carbon dating and radioactive decay 25 January 2010 17:43 UTC www.furryelephant.com [Source type: Original source]

.209Bi), to 10−23 seconds for highly unstable ones.^ Put another way, one millirad is 1 x 10-8 (0.00000001) of one watt for one second absorbed by every gram of exposed tissue.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ A disintegration means the decay or breakdown of an individual unstable nucleus, so 1 curie = 3.7 x 10 10 becquerel of unstable nuclei decaying per second.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ So one millirad = 100/ 10,000,000 x 1/1000 of one watt for one second — absorbed by every gram of tissue exposed to the radiation.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

.The factor of ln2 in the above relations results from the fact that concept of "half life" is merely a way of selecting a different base other than the natural base e for the life time expression.^ I have a easier time that suffering is rampant in each own universe and michcosom of each life and others by mental illness in various forms.
• Schizophrenia.com Support Forums: do you believe in god and religion? ... 25 January 2010 17:43 UTC www.schizophrenia.com:8080 [Source type: Original source]

^ The shorter the half-life of the radionuclide, the more atoms of this radionuclide will decay per unit time for a given mass of radionuclide.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

^ Likewise, knowledge of a radionuclide’s half-life is important for doctors and other health professionals when using radioactive substances to diagnose or treat diseases.
• Unit 2 - Lesson 2 Reading (OCRWM Curriculum) 25 January 2010 17:43 UTC www.ocrwm.doe.gov [Source type: FILTERED WITH BAYES]

.The time constant τ is the "1/e" life (time till only 1/e = about 36.8% remains) rather than the "1/2" life of a radionuclide where 50% remains (thus, τ is longer than t½).^ A variation in the radius x thus could mean a variation of the fine structure constant while the gravitational constant, Plancks constant, and the speed of light c remain the same.
• A Mechanism for Accelerated Radioactive Decay 25 January 2010 17:43 UTC www.creationresearch.org [Source type: Academic]

^ In June, The Times reported that a Philadelphia hospital gave the wrong radiation dose to more than 90 patients with prostate cancer  and then kept quiet about it.
• The Radiation Boom - Radiation Offers New Cures, and Ways to Do Harm - Series - NYTimes.com 25 January 2010 17:43 UTC www.nytimes.com [Source type: News]

^ So there would be a piece of information > > > > about the particle which is inaccessible rather than > > > > non-existent.
• Radioactive decay and the myth of randomness - sci.logic | Google Groups 25 January 2010 17:43 UTC groups.google.com [Source type: FILTERED WITH BAYES]

Thus, the following equation can easily be shown to be valid.
$N(t) = N_0\,e^{-t/ au} =N_0\,2^{-t/t_{1/2}}. \,\!$
.Since radioactive decay is exponential with a constant probability, each process could as easily be described with a different constant time period which (for example) gave its "1/3 life" (how long until only 1/3rd is left) or "1/10 life" (a time period till only 10% is left) and so on.^ The half-life of a radioactive element is the time needed for half of the material to decay.
• Half-Life of a Radioactive Element - Wolfram Demonstrations Project 3 February 2010 18:018 UTC demonstrations.wolfram.com [Source type: FILTERED WITH BAYES]

^ The radioactivity from a radioisotope is measured over a period of time .
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ It's interesting how for most of us, being a parent unites left and right on some issues with this one being an excellent example.
• Roman Polanski Has a Lot of Friends 25 January 2010 17:43 UTC www.thenation.com [Source type: General]

Thus the choice of τ and t½ for marker-times, are only for convenience, and from convention. .They reflect a fundamental principle only in so much as they show that the same proportion of a given radioactive substance will decay, during any time-period that one chooses.^ The radioactivity from a radioisotope is measured over a period of time .
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ For their benefit we now develop estimates of the health effects expected during that time period, from one year's operation of a large power plant 8 : .
• HAZARDS OF HIGH-LEVEL RADIOACTIVE WASTE — THE GREAT MYTH 3 February 2010 18:018 UTC www.phyast.pitt.edu [Source type: FILTERED WITH BAYES]

^ Cancer that has recurred (come back), usually after a period of time during which the cancer could not be detected.
• Dictionary of Cancer Terms - National Cancer Institute 3 February 2010 18:018 UTC www.cancer.gov [Source type: Academic]

## Changing decay rates?

.A number of experiments have shown that decay rates of naturally-occurring radioisotopes (for decay modes other than electron capture) are, to a high degree of precision, unaffected by external conditions such as temperature, pressure, the chemical environment and electric, magnetic or gravitational fields.^ It is also slightly lower than what you would expect if you lived in an area with naturally elevated background radiation- which some studies have shown to actually produce a slight decrease in cancer rates.
• Slashdot | Another Crumbling Reactor Springs a Tritium Leak 25 January 2010 17:43 UTC slashdot.org [Source type: FILTERED WITH BAYES]

^ Some of these particles are captured by the magnetic fields of the planets, forming their magnetospheres.
• Atmospheric Chemistry Glossary 25 January 2010 17:43 UTC www.shsu.edu [Source type: Academic]

^ The mode of decay is a low energy beta-particle (electron) which is effectively attenuated by a sheet of paper or a thin layer of dead skin.
• Slashdot | Another Crumbling Reactor Springs a Tritium Leak 25 January 2010 17:43 UTC slashdot.org [Source type: FILTERED WITH BAYES]

.Comparison of laboratory experiments over the last century, studies of the Oklo natural nuclear reactor, and astrophysical observations of the luminosity decays of distant supernovae (which occurred long ago as the light has taken a great deal of time to reach us), for example, strongly indicate that decay rates have been constant (at least to within the limitations of small experimental errors) as a function of time as well.^ The rate of polarization buildup as a function of polarizing time.
• Glossary - T 25 January 2010 17:43 UTC www.spwla.org [Source type: Reference]

^ The quantum theory allows energy to appear out of nothing, in the form of pairs of virtual particles, such as electrons and positrons, as long as the virtual pairs annihilate within a small time interval given by the uncertainty principle.
• A Mechanism for Accelerated Radioactive Decay 25 January 2010 17:43 UTC www.creationresearch.org [Source type: Academic]

^ The probability that particles will disintegrate in the time interval is given by ], where is the initial number of nuclei present and is the decay constant characteristic of the radioactive isotope.
• Radioactive Decay as a Probability Distribution - Wolfram Demonstrations Project 25 January 2010 17:43 UTC demonstrations.wolfram.com [Source type: FILTERED WITH BAYES]

.On the other hand, some recent results suggest the possibility that decay rates might have a very weak dependence (0.1% or less) on environmental factors.^ I hope some research is done on the decay rates for those.
• FARK.com: (3837248) Radioactive decay rates depend on the Earth-Sun distance..... wait... WHAT?? 25 January 2010 17:43 UTC www.fark.com [Source type: FILTERED WITH BAYES]

^ Kome : I hope some research is done on the decay rates for those.
• FARK.com: (3837248) Radioactive decay rates depend on the Earth-Sun distance..... wait... WHAT?? 25 January 2010 17:43 UTC www.fark.com [Source type: FILTERED WITH BAYES]

^ Reply Thomas says: March 20, 2008 at 10:08 am I was told that some prisoners lacked tools and had to dig with their bare hands resulting in finger loss and other deformations.
• English Russia » The Radioactive Mines 3 February 2010 18:018 UTC englishrussia.com [Source type: FILTERED WITH BAYES]

.It has been suggested that measurements of decay rates of silicon-32, manganese-54 and radium-226 exhibit small seasonal variations (about 0.1%), proposed to be related to either solar flare activity or distance from the sun.^ The half life of radium-226, in the decay chain of uranium-238, is 1600 years.
• La. workers: Exxon hid radiation risk of cleaning job - Democratic Underground 25 January 2010 17:43 UTC www.democraticunderground.com [Source type: FILTERED WITH BAYES]

^ How is this related to your proposed scheme of introducing a hidden variable?
• Radioactive decay and the myth of randomness - sci.logic | Google Groups 25 January 2010 17:43 UTC groups.google.com [Source type: FILTERED WITH BAYES]

^ Activity measure unit in the Si (Si - the International System of Units, the most widely used system of units) is the decay per second (decay/sec).
• Chernobyl - Tschernobyl - Information 25 January 2010 17:43 UTC www.chernobyl.info [Source type: Academic]

[3][4][5] .However, such measurements are highly susceptible to systematic errors, and a subsequent paper [6] has found no evidence for such correlations in a half-dozen isotopes, and sets upper limits on the size of any such effects.^ However, limited information from children employed as miners in China do not provide evidence of increased susceptibility to the effects of exposure to radon.
• ProjectDisaster » Blog Archive » ATSDR: Radon Fact Sheet 25 January 2010 17:43 UTC projectdisaster.com [Source type: FILTERED WITH BAYES]

^ No element higher than uranium ( 92 U ) is found in nature except for traces of neptunium ( 93 Np ) and plutonium ( 94 Pu ) isotopes.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

^ Outside of this sanctifying life, outside the Church, are found the errors, confusion and misunderstanding of which this literal idea “call no man father” is but one of so many examples.
• Schizophrenia.com Support Forums: do you believe in god and religion? ... 25 January 2010 17:43 UTC www.schizophrenia.com:8080 [Source type: Original source]

.An exception is the decay mode known as electron capture exhibited by a small number of nuclides.^ The mode of decay is a low energy beta-particle (electron) which is effectively attenuated by a sheet of paper or a thin layer of dead skin.
• Slashdot | Another Crumbling Reactor Springs a Tritium Leak 25 January 2010 17:43 UTC slashdot.org [Source type: FILTERED WITH BAYES]

^ The set of known or postulated nuclides that have the same number of nucleons.

.Chemical bonds can affect the rate of electron capture to a small degree (generally less than 1%) depending on the proximity of electrons to the nucleus.^ The saturated lapse rate is always less than the dry rate because the lapse rate (cooling) is less for air that contains water vapor which releases its latent heat as it cools, suppressing the cooling.
• Atmospheric Chemistry Glossary 25 January 2010 17:43 UTC www.shsu.edu [Source type: Academic]

^ It also occurs as a natural mineral in the ground, as do other poisonous chemicals for which a lethal dose is less than one ounce.
• HAZARDS OF HIGH-LEVEL RADIOACTIVE WASTE — THE GREAT MYTH 3 February 2010 18:018 UTC www.phyast.pitt.edu [Source type: FILTERED WITH BAYES]

For example in 7Be, a difference of 0.9% has been observed between half-lives in metallic and insulating environments.[7] .This relatively large effect is due to the fact that beryllium is a small atom whose valence electrons are in 2s atomic orbitals which penetrate the nucleus, and thus are subject to electron capture.^ Positrons are bound to this nucleus in atomic orbitals.

^ An atom-like system composed of a positron and an electron whose spins are antiparallel, in a singlet state.

^ When large atomic nuclei are hit with neutrons they can become highly unstable if the neutron is absorbed by the nucleus.
• Radioactivity properties & uses of alpha, beta & gamma radiation, nuclear fusion, nuclear fission, radioactive decay, half-life calculations, nuclear energy power 25 January 2010 17:43 UTC www.docbrown.info [Source type: FILTERED WITH BAYES]

## Notes

1. ^ a b "Decay and Half Life". Retrieved 2009-12-14.
2. ^ This symbol is included in ISO 21482:2007. ISO International Standards are protected by copyright and may be purchased from ISO or its members (please visit www.iso.org for more information). ISO has not reviewed the accuracy or veracity of this information.
3. ^ The mystery of varying nuclear decay, Physics World, October 2, 2008 Physicsworld.com
4. ^ Perturbation of Nuclear Decay Rates During the Solar Flare of 13 December 2006, preprint available at arXiv.org e-Print archive
5. ^ J. H. Jenkins et al., Evidence of correlations between nuclear decay rates and Earth–Sun distance, Astroparticle Physics, Volume 32, Issue 1, August 2009, Pages 42-46. Preprint available at arXiv.org e-Print archive
6. ^ E. B. Norman et al., Evidence against correlations between nuclear decay rates and Earth–Sun distance, Astroparticle Physics Volume 31, Issue 2, March 2009, Pages 135-137, available online at University of California, Berkeley
7. ^ B.Wang et al., Euro. Phys. J. A 28, 375-377 (2006) Change of the 7Be electron capture half-life in metallic environments

# Simple English

[[File:|thumb|right|150px|The trefoil symbol is used to indicate radioactive material.]]

Radioactive decay is the process where the nucleus of an atom changes into another type of nucleus and produces a particle at the same time. Nuclei which change like this are called radioactive or unstable. This change happens to the nucleus of an atom. Most atoms on earth are not radioactive, but atoms with more or less neutrons than a stable atom, that is, different isotopes of the same element, can be radioactive. For example, most carbon atoms in the world have six protons and six neutrons in their nucleus. This carbon is called carbon-12, because 12 is the number of protons and neutrons. Carbon's atomic weight is 12. If two more neutrons are added to carbon-12, it becomes carbon-14. Carbon-14 is still chemically carbon, because carbon is defined by having six protons, which it still does even after the addition of more neutrons. In fact, carbon-14 exists in all living things that contain carbon, such as animals and plants. However, it is radioactive.

Radioactive decay always changes the type of atom from an isotope that has higher energy inside its nucleus to an isotope with lower energy in its nucleus. The difference in energy between the nucleus before and after the decay is given to the particles created in the decay to increase their speed, or kinetic energy. Energy is never created or destroyed in radioactive decay.

Alpha decay, beta decay and gamma decay are the most common types of radioactive decay. They are different from each other because different types of decay produce different particles. The starting radioactive nucleus is called the parent nucleus and the nucleus that it changes into is called the daughter nucleus. The high-energy particles produced by radioactive materials are called radiation.

## Alpha decay

During alpha decay, the (physics)|atomic nucleus releases an alpha particle. The nucleus will lose two protons and two neutrons when this happens. After the decay, the atom will change to another element, because the atom loses two protons. For example, if Americium were to go through alpha decay it would change into Neptunium because Neptunium is defined by have two protons fewer than Americium. Alpha decay usually happens in heavy elements, those containing more neutrons and protons, such as uranium, thorium, plutonium, and radium.

Alpha particles cannot even go through a few centimeters of air. Alpha irradiation cannot hurt humans when the alpha source is outside the human body, because human skin does not let the alpha particles go through. Alpha radiation can be very harmful if the source is inside the body, such as when people breathe dust or gas containing materials which decay by emitting alpha particles.

## Beta decay

There are two kinds of beta decay, beta-plus and beta-minus.

In beta-minus decay, the nucleus gives out a negatively charged electron and a neutron changes into a proton:

$n^0 \rightarrow p^+ + e^- + \bar\left\{\nu\right\}_e$.
where
$n^0$ is the neutron
$\ p^+$ is the proton
$e^-$ is the electron
$\bar\left\{\nu\right\}_e$ is the anti-neutrino

Beta-minus decay happens in nuclear reactors.

In beta-plus decay, the nucleus releases a positron, which is like an electron but positively charged, and a proton changes into a neutron:

$\ p^+ \rightarrow n^0 + e^+ + \left\{\nu\right\}_e$.
where
$\ p^+$ is the proton
$n^0$ is the neutron
$e^+$ is the positron
$\left\{\nu\right\}_e$ is the neutrino

Beta-plus decay happens inside the sun and in some types of particle accelerators.

## Gamma decay

Gamma decay happens when a nucleus produces a high-energy packet of energy called a gamma ray. Gamma rays do not have electrical charge, but they do have angular momentum. Gamma rays are usually emitted from nuclei immediately after other types of decay. Gamma rays can be used to analyze radioactive materials, to kill bacteria in food, to find some types of disease, and to treat some kinds of cancer. Gamma rays have the highest energy of any electromagnetic wave, and gamma ray bursts in space are the most energetic releases of energy known to people, even more than supernovas.

# Citable sentences

Up to date as of December 26, 2010

Here are sentences from other pages on Radioactive decay, which are similar to those in the above article.