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praseodymiumneodymiumpromethium
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Nd

U
Appearance
silvery white, yellowish tinge
General properties
Name, symbol, number neodymium, Nd, 60
Element category lanthanide
Group, period, block n/a6, f
Standard atomic weight 144.242g·mol−1
Electron configuration [Xe] 4f4 6s2
Electrons per shell 2, 8, 18, 22, 8, 2 (Image)
Physical properties
Phase solid
Density (near r.t.) 7.01 g·cm−3
Liquid density at m.p. 6.89 g·cm−3
Melting point 1297 K, 1024 °C, 1875 °F
Boiling point 3347 K, 3074 °C, 5565 °F
Heat of fusion 7.14 kJ·mol−1
Heat of vaporization 289 kJ·mol−1
Specific heat capacity (25 °C) 27.45 J·mol−1·K−1
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 1595 1774 1998 (2296) (2715) (3336)
Atomic properties
Oxidation states 3, 2 (mildly basic oxide)
Electronegativity 1.14 (Pauling scale)
Ionization energies 1st: 533.1 kJ·mol−1
2nd: 1040 kJ·mol−1
3rd: 2130 kJ·mol−1
Atomic radius 181 pm
Covalent radius 201±6 pm
Miscellanea
Crystal structure hexagonal
Magnetic ordering paramagnetic, antiferromagnetic below 20K [1]
Electrical resistivity (r.t.) (α, poly) 643 nΩ·m
Thermal conductivity (300 K) 16.5 W·m−1·K−1
Thermal expansion (r.t.) (α, poly) 9.6 µm/(m·K)
Speed of sound (thin rod) (20 °C) 2330 m/s
Young's modulus (α form) 41.4 GPa
Shear modulus (α form) 16.3 GPa
Bulk modulus (α form) 31.8 GPa
Poisson ratio (α form) 0.281
Vickers hardness 343 MPa
Brinell hardness 265 MPa
CAS registry number 7440-00-8
Most stable isotopes
Main article: Isotopes of neodymium
iso NA half-life DM DE (MeV) DP
142Nd 27.2% 142Nd is stable with 82 neutrons
143Nd 12.2% 143Nd is stable with 83 neutrons
144Nd 23.8% 2.29×1015y α 1.905 140Ce
145Nd 8.3% 145Nd is stable with 85 neutrons
146Nd 17.2% 146Nd is stable with 86 neutrons
148Nd 5.7% 148Nd is stable with 88 neutrons
150Nd 5.6% 6.7×1018y ββ 3.367 150Sm

Neodymium (pronounced /ˌniː.ɵˈdɪmiəm/ NEE-o- DIM-ee-əm) is a chemical element with the symbol Nd and atomic number 60. It is a soft silvery metal which tarnishes in air. Neodymium was discovered in 1885. It is present in significant quantities in the ore minerals monazite and bastnäsite. Neodymium is not found naturally in metallic form or unaccompanied by other lanthanoids and it is usually refined for general use. Neodymium has several important applications: it is a constituent of neodymium magnets, which are widely used in motors, loudspeakers and numerous appliances. Neodymium is a popular additive in glass, giving it a characteristic reddish-purple color; this glass is used in lasers emitting infrared light with the wavelength of 1.054–1.062 micrometers. Neodymium is also used in Nd:YAG lasers to generate 1.064 micrometer light. This is one of the most significant solid-state lasers. Neodymium is a key component of an alloy used to make high-power lightweight magnets for electric motors of hybrid cars, and in generators for wind turbines.[2]

Contents

Characteristics

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Physical

Neodymium, a rare earth metal, was present in classical mischmetal to the extent of about 18%. The metal has a bright, silvery metallic luster; however, as one of the more reactive rare earth (lanthanide) metals, it quickly oxidizes in air. The oxide layer then falls off, which exposes the metal to further oxidation. Thus a centimeter-sized Nd sample completely oxidizes within a year.[3]

Neodymium exists in two allotropic forms, with a transformation from a double hexagonal to a body-centered cubic structure taking place at 863 °C.[4]

Chemical

Neodymium metal tarnishes slowly in air and burns readily at 150 °C to form neodymium(III) oxide:

4 Nd + 3 O2 → 2 Nd2O3

Neodymium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form neodymium hydroxide:

2 Nd (s) + 6 H2O (l) → 2 Nd(OH)3 (aq) + 3 H2 (g)

Neodymium metal reacts with all the halogens:

2 Nd (s) + 3 F2 (g) → 2 NdF3 (s) [violet]
2 Nd (s) + 3 Cl2 (g) → 2 NdCl3 (s) [mauve]
2 Nd (s) + 3 Br2 (g) → 2 NdBr3 (s) [violet]
2 Nd (s) + 3 I2 (g) → 2 NdI3 (s) [green]

Neodymium dissolves readily in dilute sulfuric acid to form solutions containing the lilac Nd(III) ions, which exist as a [Nd(OH2)9]3+ complexes:[5]

2 Nd (s) + 3 H2SO4 (aq) → 2 Nd3+ (aq) + 3 SO 2−4 (aq) + 3 H2 (g)

Compounds

Neodymium compounds include

  • Halides: NdF3, NdCl3, NdBr3, NdI3
  • Oxides: Nd2O3
  • Sulfides: NdS, Nd2S3
  • Nitrides: NdN

Isotopes

Naturally occurring neodymium is composed of 5 stable isotopes, 142Nd, 143Nd, 145Nd, 146Nd and 148Nd, with 142Nd being the most abundant (27.2% natural abundance), and 2 radioisotopes, 144Nd and 150Nd. In all, 31 radioisotopes of neodymium have been characterized up to now, with the most stable being naturally occurring isotopes 144Nd (alpha decay, a half-life (T½) of 2.29×1015 years) and 150Nd (double beta decay, T½ = 7×1018 years). All of the remaining radioactive isotopes have half-lives that are less than 11 days, and the majority of these have half-lives that are less than 70 seconds. This element also has 13 known meta states with the most stable being 139mNd (T½ = 5.5 hours), 135mNd (T½ = 5.5 minutes) and 133m1Nd (T½ ~ 70 seconds).

The primary decay modes before the most abundant stable isotope, 142Nd, are electron capture and positron decay, and the primary mode after is beta minus decay. The primary decay products before 142Nd are element Pr (praseodymium) isotopes and the primary products after are element Pm (promethium) isotopes.

History

Neodymium was discovered by Baron Carl Auer von Welsbach, an Austrian chemist, in Vienna in 1885. He separated neodymium, as well as the element praseodymium, from a material known as didymium by means of fractional crystallization of the double ammonium nitrate tetrahydrates from nitric acid, while following the separation by spectroscopic analysis; however, it was not isolated in relatively pure form until 1925. The name neodymium is derived from the Greek words neos (νέος), new, and didymos (διδύμος), twin.[6]

Double nitrate crystallization was the means of commercial neodymium purification until the 1950s. Lindsay Chemical Division was the first to commercialize large-scale ion-exchange purification of neodymium. Starting in the 1950s, high purity (above 99%) neodymium was primarily obtained through an ion exchange process from monazite, a mineral rich in rare earth elements. The metal itself is obtained through electrolysis of its halide salts. Currently, most neodymium is extracted from bastnäsite, (Ce,La,Nd,Pr)CO3F, and purified by solvent extraction. Ion-exchange purification is reserved for preparing the highest purities (typically >99.99 %). The evolving technology, and improved purity of commercially available neodymium oxide, was reflected in the appearance of neodymium glass that resides in collections today. Early neodymium glass made in the 1930s, have a more reddish or orange tinge than modern versions, which are more cleanly purple, due to the difficulties in removing the last traces of praseodymium when the fractional crystallization technology had to be relied on.

Occurrence and production

Bastnäsite

Neodymium is never found in nature as the free element; rather, it occurs in ores such as monazite and bastnäsite that contain small amounts of all the rare earth metals. The main mining areas are China, United States, Brazil, India, Sri Lanka and Australia; and reserves of neodymium are estimated at about 8 million tonnes. Although it belongs to "rare earth metals," neodymium is not rare at all - its abundance in the Earth crust is about 38 mg/kg, which is the second among rare-earth elements after cerium. The world production of neodymium is about 7,000 tonnes per year.[6] The bulk of current production is from China, whose government has recently imposed strategic materials controls on the element, raising some concerns in consuming countries.[7]

Neodymium typically comprises 10 to 18% of the rare earth content of commercial orebodies of the light rare earth element (LREE) dominant minerals bastnasite and monazite. With neodymium being the most strongly colored trivalent lanthanoid, that level of neodymium can occasionally dominate the coloration of rare earth minerals, when competing chromophores are absent, and provide a pink coloration. Outstanding examples of this include monazite crystals from the tin veins of Llallagua, Bolivia, ancylite from Mont Saint-Hilaire, Quebec, or lanthanite from the Saucon Valley of Pennsylvania. As with neodymium glass, such minerals change color under the differing lighting conditions. The absorption bands of neodymium interact with the visible mercury vapor emission spectrum, such that unfiltered shortwave UV light causes neodymium-containing minerals to reflect a distinct green color. This can be observed with monazite-containing sands or bastnasite-containing ore.

Applications

Neodymium magnet on a bracket from a hard drive.
  • Neodymium magnets are the strongest permanent magnets known - Nd2Fe14B. These magnets are cheaper, lighter, and stronger than samarium-cobalt magnets. Neodymium magnets appear in products such as microphones, professional loudspeakers, in-ear headphones, guitar and bass guitar pick-ups and computer hard disks where low mass, small volume, or strong magnetic fields are required. Neodymium magnet electric motors have also been responsible for the development of purely electrical model aircraft within the first decade of the 21st century, to the point that these are displacing internal combustion powered models internationally. Likewise, due to this high magnetic-flux capacity, it is heavily used in the electric motors of hybrid automobiles and in the electricity generators of commercial wind turbine generators.
  • Neodymium is a component of didymium used for coloring glass to make welder's and glass-blower's goggles. The sharp absorption bands obliterate the strong sodium emission at 589 nm.
  • Neodymium has an unusually large specific heat capacity at liquid-helium temperatures, so is useful in cryocoolers
  • Neodymium lamps are incandescent lamps containing neodymium in the glass to filter out yellow light, resulting in a whiter light more like sunlight
  • Neodymium colors glass in delicate shades ranging from pure violet through wine-red and warm gray. Light transmitted through such glass shows unusually sharp absorption bands; the glass is used in astronomical work to produce sharp bands by which spectral lines may be calibrated. Neodymium is also used to remove the green color caused by iron contaminants from glass. Neodymium and didymium glass are used in color-enhancing filters in photography.
  • Neodymium salts are used as a colorant for enamels.
  • Probably because of similarities to Ca2+, Nd3+ has been reported[8] to promote plant growth. Rare earth element compounds are frequently used in China as fertilizer.
  • Samarium-neodymium dating is useful for determining the age relationships of rocks[9] and meteorites.
  • Size and strength of volcanic eruption can be predicted by scanning for neodymium isotopes. Small and large volcanic eruptions produce lava with different neodymium isotope composition. From the composition of isotopes, scientists predict how big the coming eruption will be, and use this information to warn residents of the intensity of the eruption.
  • Certain transparent materials with a small concentration of neodymium ions can be used in lasers as gain media for infrared wavelengths (1054-1064 nm), e.g. Nd:YAG (yttrium aluminium garnet), Nd:YLF (yttrium lithium fluoride), Nd:YVO4 (yttrium orthovanadate), and Nd:glass. The current laser at the UK Atomic Weapons Establishment (AWE), the HELEN (High Energy Laser Embodying Neodymium) 1-terawatt neodymium-glass laser, can access the midpoints of pressure and temperature regions and is used to acquire data for modeling on how density, temperature and pressure interact inside warheads. HELEN can create plasmas of around 106 K, from which opacity and transmission of radiation are measured.[10]

Neodymium glass

Neodymium doped glass slabs used in extremely powerful lasers for inertial confinement fusion.

Neodymium glass (Nd:glass) is produced by the inclusion of neodymium oxide (Nd2O3) in the glass melt. In daylight or incandescent light neodymium glass appears lavender, but it appears pale blue under fluorescent lighting.

Neodymium glass solid-state lasers are used in extremely high power (terawatt scale), high energy (megajoules) multiple beam systems for inertial confinement fusion (see last bulleted paragraph above). Nd:glass lasers are usually frequency tripled to the third harmonic at 351 nm in laser fusion devices.

Neodymium glass is becoming widely used in incandescent light bulbs, to provide a more "natural" light. It has been patented for use in automobile rear-view mirrors, to reduce the glare at night.

The first commercial use of purified neodymium was in glass coloration, starting with experiments by Leo Moser in November 1927. The resulting "Alexandrite" glass remains a signature color of the Moser glassworks to this day. Neodymium glass was widely emulated in the early 1930s by American glasshouses, most notably Heisey, Fostoria ("wisteria"), Cambridge ("heatherbloom"), and Steuben ("wisteria"), and elsewhere (e.g. Lalique, in France, or Murano). Tiffin's "twilight" remained in production from about 1950 to 1980.[11] Current sources include glassmakers in the Czech Republic, the United States, and China.

The sharp absorption bands of neodymium cause the glass color to change under different lighting conditions, being reddish-purple under daylight or yellow incandescent light, but blue under white fluorescent lighting, or greenish under trichromatic lighting. This color-change phenomenon is highly prized by collectors. In combination with gold or selenium, beautiful red colors result. Since neodymium coloration depends upon "forbidden" f-f transitions deep within the atom, there is relatively little influence on the color from the chemical environment, so the color is impervious to the thermal history of the glass. However, for the best color, iron-containing impurities need to be minimized in the silica used to make the glass. The same forbidden nature of the f-f transitions makes rare-earth colorants less intense than those provided by most d-transition elements, so more has to be used in a glass to achieve the desired color intensity. The original Moser recipe used about 5% of neodymium oxide in the glass melt, a sufficient quantity such that Moser referred to these as being "rare earth doped" glasses. Being a strong base, that level of neodymium would have affected the melting properties of the glass, and the lime content of the glass might have had to be adjusted accordingly.[12]

Precautions

Neodymium metal dust is a combustion and explosion hazard. Neodymium compounds, as with all rare earth metals, are of low to moderate toxicity; however its toxicity has not been thoroughly investigated. Neodymium dust and salts are very irritating to the eyes and mucous membranes, and moderately irritating to skin. Breathing the dust can cause lung embolisms, and accumulated exposure damages the liver. Neodymium also acts as an anticoagulant, especially when given intravenously.[6]

Neodymium magnets have been tested for medical uses such as magnetic braces and bone repair, but biocompatibility issues have prevented widespread application. Commercially available magnets made from neodymium are exceptionally strong, and can attract each other from large distances. If not handled carefully, they come together very quickly and forcefully, causing injuries. For example, a person lost part of his finger when two magnets he was using snapped together from 50 cm away.[13] Another danger is when two such magnets snap together, the force of the collision can cause them to shatter, sending sharp pieces flying around, potentially causing serious injuries.[6]

See also

References

  1. ^ Gschneidner, K.A., and Eyring, L., Handbook on the Physics and Chemistry of Rare Earths, North Holland Publishing Co., Amsterdam, 1978.
  2. ^ Steve Gorman, As hybrid cars gobble rare metals, shortage looms, Reuters, Mon Aug 31, 2009
  3. ^ "Rare-Earth Metal Long Term Air Exposure Test". http://www.elementsales.com/re_exp/index.htm. Retrieved 2009-08-08.  
  4. ^ C. R. Hammond (2000). The Elements, in Handbook of Chemistry and Physics 81th edition. CRC press. ISBN 0849304814.  
  5. ^ "Chemical reactions of Neodymium". Webelements. https://www.webelements.com/neodymium/chemistry.html. Retrieved 2009-06-06.  
  6. ^ a b c d John Emsley (2003). Nature's building blocks: an A-Z guide to the elements. Oxford University Press. pp. 268–270. ISBN 0198503407. http://books.google.com/books?id=j-Xu07p3cKwC.  
  7. ^ Concern as China clamps down on rare earth exports (The Independent, UK news site)
  8. ^ Y. Wei et al. "The Effect of Neodymium (Nd3+) on Some Physiological Activities in Oilseed Rape during Calcium (Ca2+) Starvation" 10th International Rapeceed Congress
  9. ^ "Team finds Earth's 'oldest rocks'". BBC news. http://news.bbc.co.uk/2/hi/science/nature/7639024.stm. Retrieved 2009-06-06.  
  10. ^ Norman, Michael J.; Andrew, James E.; Bett, Thomas H.; Clifford, Roger K.; England, John E.; Hopps, Nicholas W.; Parker, Kenneth W.; Porter, Kenneth; Stevenson, Mark (2002). "Multipass Reconfiguration of the HELEN Nd:Glass Laser at the Atomic Weapons Establishment". Applied Optics 41: 3497. doi:10.1364/AO.41.003497.  
  11. ^ "Chameleon Glass Changes Color". http://coloradosprings.yourhub.com/CrippleCreekTellerCounty/Stories/Arts/Story~443258.aspx. Retrieved 2009-06-06.  
  12. ^ Charles Bray (2001). Dictionary of glass: materials and techniques. University of Pennsylvania Press. p. 102. ISBN 081223619X. http://books.google.com/books?id=KbZkxDyeG18C&pg=PA102.  
  13. ^ Swain, Frank (March 6, 2009). "How to remove a finger with two super magnets". Seed Media Group LLC. http://scienceblogs.com/sciencepunk/2009/03/how_to_remove_a_finger_with_tw.php. Retrieved 2009-06-28.  

Books

  • "The Industrial Chemistry of the Lanthanons, Yttrium, Thorium and Uranium", by R.J. Callow, Pergamon Press 1967.
  • Lindsay Chemical Division, American Potash and Chemical Corporation, Price List, 1960.
  • "Chemistry of the Lanthanons", by R.C. Vickery, Butterworths 1953.

External links


Simple English

Neodymium is a chemical element that has the symbol Nd on the periodic table. It has the atomic number 60 which means it has 60 protons in an atom. Most likely known as a magnet.



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