62
  Sm  
150.360000
Samarium

Name: Samarium
Symbol: Sm
Atomic Number: 62
Atomic Weight: 150.360000
Family: Rare Earth Elements
CAS RN: 7440-19-9
Description: A silvery white rare earth metal.
State (25C): Solid
Oxidation states: +2, +3

Molar Volume: 19.95 cm3/mole
Valence Electrons: 4f66s2

Boiling Point: 2067oK, 1794oC, 3261oF
Melting Point:
1345oK, 1072oC, 1962oF
Electrons Energy Level: 2, 8, 18, 24, 8, 2
Isotopes: 38 + 5 Stable + 5 meta states
Heat of Vaporization: 165 kJ/mol
Heat of Fusion: 8.62 kJ/mol
Density: 7.52g/cm3 @ 300oK
Specific Heat: 0.2 J/goK
Atomic Radius: 2.59
Ionic Radius: 0.964
Electronegativity: 1.17 (Pauling), 1.07 (Allrod Rochow)
Vapor Pressure: 563 Pa @ 1072C
57
La
138.9
58
Ce
140.1
59
Pr
140.9
60
Nd
144.2
61
Pm
(145)
62
Sm
150.4
63
Eu
152.0
64
Gd
157.3
65
Tb
158.9
66
Dy
162.5
67
Ho
164.9
68
Er
167.3
69
Tm
168.9
70
Yb
173.0
71
Lu
175.0

1s2 2s2p6 3s2p6d10 4s2p6d10f6 5s2p6 6s2

History

Named for the mineral samarskite from which it is extracted.   Samarium was first discovered spectroscopically, in a material known as dydimia, in 1853 by Swiss chemist Jean Charles Galissard de Marignac by its sharp absorption lines in didymium and isolated and identified in Paris in 1879 by French chemist Paul Emile Lecoq de Boisbaudran from the mineral samarskite (Y,Ce,U,Fe)3(Nb,Ta,Ti)5O16.

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.

The pure metal has a silver lustre and tarnishes slowly at room conditions. It is readily magnetized and holds its magnetism extremely well. Rare earth magnets (samarium-cobalt, for example) exploit this property.

Although it is present in samarskite, commercial production of samarium is from monazite sand, (Ce, La, Th, Nd, Y)PO4, which can contain as much as 2.8% Sm by weight.

Characteristics

Samarium is a rare earth metal, with a bright silver luster, that is reasonably stable in air; it ignites in air at 150C.  Even with long-term storage under mineral oil, samarium is gradually oxidized, with a grayish-yellow powder of the oxide-hydroxide being formed.  Three crystal modifications of the metal also exist, with transformations at 734 and 922C.

1s2
2s2 2p6
3s2 3p6 3d10
4s2 4p6 4d10 4f6
5s2 5p6
6s2

The sulfide has excellent high-temperature stability and good thermoelectric efficiencies up to 1100oC.

Occurrence

Samarium is never found free in nature, but, like other rare earth elements, is contained in many minerals, including monazite, bastnasite and samarskite; monazite (in which it occurs up to an extent of 2.8%) and bastnasite are also used as commercial sources.  Misch metal 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.

Applications

Samarium is one of the rare earth elements used to make carbon arc lights which are used in the motion picture industry for studio lighting and projector lights. Samarium also makes up about 1% of Misch metal, a material that is used to make flints for lighters.

Ion-exchange and solvent extraction techniques have recently simplified separation of the rare earths from one another; more recently, electrochemical deposition, using an electrolytic solution of lithium citrate and a mercury electrode, is said to be a simple, fast, and highly specific way to separate the rare earths. Samarium metal can be produced by reducing the oxide with lanthanum.

Compounds

Samarium forms a compound with cobalt (SmCo5) which is a powerful permanent magnet with the highest resistance to demagnetization of any material known.   Samarium oxide (Sm2O3) is added to glass to absorb infrared radiation and acts as a catalyst for the dehydration and dehydrogenation of ethanol (C2H6O).

Fluorides Chlorides Bromides Iodides
SmF2
SmF3
SmCl2
SmCl3
SmBr2
SmBr3
SmI2
SmI3
Oxides Sulfides Selenides Tellurides
Sm2O3 Sm2S3 Sm2Se3 Sm2Te3

Isotopes

Naturally occurring samarium is composed of 5 stable isotopes144Sm, 150Sm, 152Sm and 154Sm, and 3 radioisotopes, 147Sm, 148Sm and 149Sm, with 152Sm being the most abundant (26.75% natural abundance.  38 radioisotopes have been characterized, with the most stable being 148Sm with a half-life of 7x1015 years, 149Sm with a half-life of more than 2x1015 years, and 147Sm with a half-life of 1.06x1011 years.  All of the remaining radioactive isotopes have half-lifes that are less than 1.04x108 years, and the majority of these have half lifes that are less than 48 seconds. This element also has 5 meta states with the most stable being 141mSm (t 22.6 minutes), 143m1Sm (t 66 seconds) and 139mSm (t 10.7 seconds).

The primary decay mode before the most abundant stable isotope, 152Sm, is electron capture, and the primary mode after is beta minus decay.  The primary decay products before 152Sm are element Pm (promethium) isotopes, and the primary products after are element Eu (europium) isotopes.

atom.gif (700 bytes)

Isotope  
Atomic Mass
 
Half-Life
128Sm 127.95808 ~0.5 seconds
129Sm 128.95464 550 ms
130Sm 129.94892 ~1 seconds
131Sm 130.94611 1.2 seconds
132Sm 131.94069 4.0 seconds
133Sm 132.93867 2.90 seconds
134Sm 133.93397 10 seconds
135Sm 134.93252 10.3 seconds
135mSm   2.4 seconds
136Sm 135.928276 47 seconds
137Sm 136.92697 45 seconds
137mSm   ~20 seconds
138Sm 137.923244 3.1 minutes
139Sm 138.922297 2.57 minutes
139mSm   10.7 seconds
140Sm 139.918995 14.82 minutes
141Sm 140.918476 10.2 minutes
141mSm   22.6 minutes
142Sm 141.915198 72.49 minutes
143Sm 142.914628 8.75 minutes
143m1Sm   66 seconds
144Sm 143.911999 Stable
145Sm 144.913410 340 days
146Sm 145.913041 1.03 x 108 years
147Sm 146.9148979 106.0 x 1012 years
148Sm 147.9148227 7 x 1015 years
149Sm 148.9171847 Stable
150Sm 149.9172755 Stable
151Sm 150.9199324 90 years
152Sm 151.9197324 Stable
153Sm 152.9220974 46.284 hours
154Sm 153.9222093 Stable
155Sm 154.9246402 22.3 minutes
156Sm 155.925528 9.4 hours
157Sm 156.92836 8.03 minutes
158Sm 157.92999 5.30 minutes
159Sm 158.93321 11.37 seconds
160Sm 159.93514 9.6 seconds
161Sm 160.93883 4.8 seconds
162Sm 161.94122 2.4 seconds
163Sm 162.94536 ~1 seconds
164Sm 163.94828 ~500 ms
165Sm 164.95298 ~200 ms

Precautions

80px-Flammable.jpg (2186 bytes) As with the other lanthanides, samarium compounds are of low to moderate toxity, although their toxicity has not been investigated in detail.  It ignites in air at 150C.

atom.gif (700 bytes)

Samarium Data

 

Atomic Structure

Atomic Radius (): 2.59
Atomic Volume cm3/mol : 19.95cm3/mol
Covalent Radius: 1.62
Crystal Structure: Rhombohedral
Ionic Radius: 0.964

Chemical Properties

Electrochemical Equivalents: 1.87g/amp-hr
Electron Work Function: 2.7eV
Electronegativity: 1.17 (Pauling); 1.07 (Allrod Rochow)
Heat of Fusion: 8.63 kJ/mol
First Ionization Potential: 5.64
Second Ionization Potential: 11.069
Third Ionization Potential: 23.423
Valence Electron Potential: 44.8 -eV
Ionization Energy (eV): unknown

Physical Properties

Atomic Mass Average: 150.36
Boiling Point: 2067K, 1794C,  3261F
Melting Point: 1347K, 1074C, 1965F
Heat of Vaporization: 166.4 kJ/mol
Coefficient of Lineal Thermal Expansion/K-1: 10.4E-6
Electrical Conductivity: 0.00956 106/cm
Thermal Conductivity: 0.133 W/cmK
Density: 7.52g/cm3 @ 300oK
Enthalpy of Atomization: 209 kJ/mole @ 25C
Enthalpy of Fusion: 8.62 kJ/mole
Enthalpy of Vaporization: 166.4 kJ/mole
Molar Volume: 19.95 cm3/mole
Specific Heat: 0.2 J/gK or 0.180 J/g mol
Vapor Pressure: 563 Pa @ 1072C
Estimated Crustal Abundance: 7.05 milligrams per kilogram
Estimated Oceanic Abundance: 4.510-7 milligrams per liter

Miscellaneous

Fusion Heat (kJ/mol): 8.9
Debye Temperature (K): 166.00
First Ionizing Energy (kJ/mol): 540.1
Lattice Structure: Rhombohedral (RHL)
Lattice Constant (): 9.000