Samarium: Wikis

  
  
  

Note: Many of our articles have direct quotes from sources you can cite, within the Wikipedia article! This article doesn't yet, but we're working on it! See more info or our list of citable articles.

Encyclopedia

From Wikipedia, the free encyclopedia

promethiumsamariumeuropium
-

Sm

Pu
Appearance
silvery white
General properties
Name, symbol, number samarium, Sm, 62
Element category lanthanide
Group, period, block n/a6, f
Standard atomic weight 150.36g·mol−1
Electron configuration [Xe] 6s2 4f6
Electrons per shell 2, 8, 18, 24, 8, 2 (Image)
Physical properties
Phase solid
Density (near r.t.) 7.52 g·cm−3
Liquid density at m.p. 7.16 g·cm−3
Melting point 1345 K, 1072 °C, 1962 °F
Boiling point 2067 K, 1794 °C, 3261 °F
Heat of fusion 8.62 kJ·mol−1
Heat of vaporization 165 kJ·mol−1
Specific heat capacity (25 °C) 29.54 J·mol−1·K−1
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 1001 1106 1240 (1421) (1675) (2061)
Atomic properties
Oxidation states 3, 2 (mildly basic oxide)
Electronegativity 1.17 (Pauling scale)
Ionization energies 1st: 544.5 kJ·mol−1
2nd: 1070 kJ·mol−1
3rd: 2260 kJ·mol−1
Atomic radius 180 pm
Covalent radius 198±8 pm
Miscellanea
Crystal structure rhombohedral
Magnetic ordering paramagnetic[1]
Electrical resistivity (r.t.) (α, poly) 0.940 µΩ·m
Thermal conductivity (300 K) 13.3 W·m−1·K−1
Thermal expansion (r.t.) (α, poly) 12.7 µm/(m·K)
Speed of sound (thin rod) (20 °C) 2130 m/s
Young's modulus (α form) 49.7 GPa
Shear modulus (α form) 19.5 GPa
Bulk modulus (α form) 37.8 GPa
Poisson ratio (α form) 0.274
Vickers hardness 412 MPa
Brinell hardness 441 MPa
CAS registry number 7440-19-9
Most stable isotopes
Main article: Isotopes of samarium
iso NA half-life DM DE (MeV) DP
144Sm 3.07% 144Sm is stable with 82 neutrons
146Sm syn 1.03×108y α 2.529 142Nd
147Sm 14.99% 1.06×1011y α 2.310 143Nd
148Sm 11.24% 7×1015y α 1.986 144Nd
149Sm 13.82% >2×1015 y α 1.870 145Nd
150Sm 7.38% 150Sm is stable with 88 neutrons
152Sm 26.75% 152Sm is stable with 90 neutrons
154Sm 22.75% 154Sm is stable with 92 neutrons

Samarium (pronounced /səˈmɛəriəm/, sə-MAIR-ee-əm) is a chemical element with the symbol Sm and atomic number 62.

Contents

Characteristics

Physical

Samarium is a rare earth metal, with a bright silver luster. Three crystal modifications of the metal also exist, with transformations at 734 and 922 °C, making it polymorphic. Individual samarium atoms can be isolated by encaspulating them into fullerene molecules.[2]

Chemical

Samarium oxidizes in air and ignites at 150 °C. Even with long-term storage under mineral oil, samarium is gradually oxidized, with a grayish-yellow powder of the oxide-hydroxide being formed. The metallic appearance of a sample can be preserved by sealing it under an inert gas such as argon.

Samarium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form samarium hydroxide:

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

Samarium metal reacts with all the halogens:

2 Sm (s) + 3 F2 (g) → 2 SmF3 (s) [white]
2 Sm (s) + 3 Cl2 (g) → 2 SmCl3 (s) [yellow]
2 Sm (s) + 3 Br2 (l) → 2 SmBr3 (s) [yellow]
2 Sm (s) + 3 I2 (s) → 2 SmI3 (s) [orange]

Samarium dissolves readily in dilute sulfuric acid to form solutions containing the pale green Sm(III) ions, which exist as a [Sm(OH2)9]3+ complexes:[3]

2 Sm (s) + 3 H2SO4 (aq) → 2 Sm3+ (aq) + 3 SO 2−4 (aq) + 3 H2 (g)

Compounds

Compounds of Samarium include:

The most common oxidation state of samarium is +3, but +2 compounds are known too, such as SmI2.

Isotopes

Naturally occurring samarium is composed of four stable isotopes, 144Sm, 150Sm, 152Sm and 154Sm, and three extremely long-lived radioisotopes, 147Sm (1.06 × 1011y), 148Sm (7 × 1015y) and 149Sm (>2 × 1015y), with 152Sm being the most abundant (26.75% natural abundance).

151Sm has a halflife of 90 years, and 145Sm has a halflife of 340 days. All of the remaining radioisotopes have half-lives that are less than 2 days, and the majority of these have half-lives that are less than 48 seconds. This element also has 5 meta states with the most stable being 141mSm (t½ 22.6 minutes), 143m1Sm (t½ 66 seconds) and 139mSm (t½ 10.7 seconds).

The long lived isotopes,146Sm, 147Sm, and 148Sm primarily decay by alpha decay to isotopes of neodymium. Lighter unstable isotopes of samarium primarily decay by electron capture to isotopes of promethium, while heavier ones decay by beta minus decay to isotopes of europium

Natural Samarium has an activity of 128 Bq/g.

History

Samarium was discovered in 1853 by Swiss chemist Jean Charles Galissard de Marignac by its sharp absorption lines in didymium, and isolated in Paris in 1879 by French chemist Paul Émile Lecoq de Boisbaudran from the mineral samarskite ((Y,Ce,U,Fe)3(Nb,Ta,Ti)5O16). Although samarskite was first found in the Urals, by the late 1870s a new deposit had been located in North Carolina, and it was from that source that the samarium-bearing didymium had originated.

The samarskite mineral was named after Vasili Samarsky-Bykhovets, the Chief of Staff (Colonel) of the Russian Corps of Mining Engineers in 1845–1861. The name of the element is derived from the name of the mineral, and thus traces back to the name Samarsky-Bykhovets. In this sense samarium was the first chemical element to be named after a living person.

Prior to the advent of ion-exchange separation technology in the 1950s, samarium had no commercial uses in pure form. However, a by-product of the fractional crystallization purification of neodymium was a mixture of samarium and gadolinium that acquired the name of "Lindsay Mix" after the company that made it. This material is thought to have been used for nuclear control rods in some of the early nuclear reactors. Nowadays, a similar commodity product has the name "samarium-europium-gadolinium" (SEG) concentrate. It is prepared by solvent extraction from the mixed lanthanides extracted from bastnäsite (or monazite). Since the heavier lanthanides have the greater affinity for the solvent used, they are easily extracted from the bulk using relatively small proportions of solvent. Not all rare earth producers who process bastnäsite do so on large enough scale to continue onward with the separation of the components of SEG, which typically makes up only one or two percent of the original ore. Such producers will therefore be making SEG with a view to marketing it to the specialized processors. In this manner, the valuable europium content of the ore is rescued for use in phosphor manufacture. Samarium purification follows the removal of the europium. Currently, being in oversupply, samarium oxide is less expensive on a commercial scale than its relative abundance in the ore might suggest.

Occurrence

Samarskite

Samarium is not found free in nature, but, like other rare earth elements, is contained in many minerals, including monazite, bastnäsite and samarskite; monazite (in which it occurs up to an extent of 2.8%) and bastnäsite are also used as commercial sources. Mischmetal containing about 1% of samarium has long been used, but it was not until recent years that relatively pure samarium has been isolated through ion exchange processes, solvent extraction techniques, and electrochemical deposition. The metal is often prepared by electrolysis of a molten mixture of samarium(III) chloride with sodium chloride or calcium chloride. Samarium can also be obtained by reducing its oxide with lanthanum.[4]

Applications

Uses of Samarium include:

Precautions

As with the other lanthanides, samarium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail.

References

  1. ^ Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81th edition, CRC press.
  2. ^ Okazaki , T (2002). "Electronic and geometric structures of metallofullerene peapods". Physica B 323: 97. doi:10.1016/S0921-4526(02)00991-2.  
  3. ^ "Chemical reactions of Samarium". Webelements. https://www.webelements.com/samarium/chemistry.html. Retrieved 2009-06-06.  
  4. ^ N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon Press, Oxford, UK, 1984.
  5. ^ Cotton (2007). Advanced inorganic chemistry, 6th ed. Wiley-India. p. 1128. ISBN 8126513381. http://books.google.com/books?id=U3MWRONWAmMC&pg=PA1128.  
  6. ^ "Centerwatch About drug Quadramet". http://www.centerwatch.com/patient/drugs/dru267.html. Retrieved 2009-06-06.  

External links


1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

SAMARIUM [[[symbol]] Sm, atomic weight 150.4 (0= 16)1, a rare earth metal (see Rare Earths). The separation has been worked at by A. v. Welsbach, L. de Boisbaudran, Urbain and Lacombe (Comptes rendus, 1903, 1 37 pp. 568, 792); Demargay (ibid. 1900, 230, p. 101q); Benedicks; Felt and Przibylla (Zeit. anorg. Chem., 1905, 43, p. 202) and others. The metal may be obtained by reduction of its oxide with magnesium. It combines with hydrogen to form a hydride. The salts are mostly of a yellowish colour. The chloride, SmC1 3.6H 2 0, is a deliquescent solid which when heated in hydrochloric acid gas to 180° C. yields the anhydrous chloride. This anhydrous chloride is reduced to a lower chloride, of composition SmC1 2, when heated to a high temperature in a current of hydrogen or ammonia (Matignon and Cazes, Coupes rendus, 2906, 142, p. 183). The chloride, SmCl 2, is a brown crystalline powder which is decomposed by water with liberation of hydrogen and the formation of the oxide, Sm 2 O 3, and an oxychloride, SmOC1. The fluoride, SmF 3 .H 2 O, was prepared by H. Moissan by acting with fluorine on the carbide. The sulphate, Sm 2 (SO 4) 3.81120, is obtained by the action of sulphuric acid on the nitrate. It forms double salts with the alkaline sulphates. The carbide, SmC2, is formed when the oxide is heated with carbon in the electric furnace.


<< Samaritans

Samarkand, Turkestan >>


Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

See also samarium

German

Chemical Element: Sm (atomical number 62)

Noun

Samarium n

  1. samarium

Simple English

Samarium is a chemical element that has the symbol Sm on the periodic table. It has the atomic number 62 which means it has 62 protons in an atom.








Got something to say? Make a comment.
Your name
Your email address
Message