Samarium Pronunciation (sə-MAIR -ee-əm ) Appearance sillery white Standard atomic weight A r, std (Sm) 7002150360000000000♠ 150.36(2)[ 1] Samarium in the periodic cairt
- ↑Sm ↓ Pu
promethium ← samarium → europium
Atomic nummer (Z ) 62 Group group n/a Period period 6 Block f-block Element category Lanthanide Electron confeeguration [Xe ] 4f6 6s2 Electrons per shell 2, 8, 18, 24, 8, 2 Pheesical properties Phase at STP solit Meltin pynt 1345 K (1072 °C, 1962 °F) Bylin pynt 2067 K (1794 °C, 3261 °F) Density (near r.t. ) 7.52 g/cm3 when liquid (at m.p. ) 7.16 g/cm3 Heat o fusion 8.62 kJ/mol Heat o vapourisation 165 kJ/mol Molar heat capacity 29.54 J/(mol·K) Vapour pressur
P (Pa)
1
10
100
1 k
10 k
100 k
at T (K)
1001
1106
1240
(1421)
(1675)
(2061)
Atomic properties Oxidation states 0,[ 2] +1, +2, +3 (a mildly basic oxide) Electronegativity Pauling scale: 1.17 Atomic radius empirical: 180 pm Covalent radius 198±8 pm Colour lines in a spectral range Spectral lines o samarium Ither properties Naitural occurrence primordial Creestal structur rhombohedral Speed o soond thin rod 2130 m/s (at 20 °C) Thermal expansion (r.t.) (α, poly) 12.7 µm/(m·K) Thermal conductivity 13.3 W/(m·K) Electrical resistivity (r.t.) (α, poly) 0.940 µ Ω·m Magnetic orderin paramagnetic[ 3] 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 haurdness 412 MPa Brinell haurdness 441 MPa CAS Nummer 7440-19-9 History Diskivery Lecoq de Boisbaudran (1879) First isolation Lecoq de Boisbaudran (1879) Main isotopes o samarium
Isotope
Abundance
Hauf-life (t 1/2 )
Decay mode
Product
144 Sm
3.07%
-
(β+ β+ )
144 Nd
(α)
140 Nd
145 Sm
syn
340 d
ε
145 Pm
146 Sm
trace
1.03×108 y
α
142 Nd
147 Sm
14.99%
1.06×1011 y
α
143 Nd
148 Sm
11.24%
7×1015 y
α
144 Nd
149 Sm
13.82%
>2×1015 y
(α)
145 Nd
150 Sm
7.38%
-
(α)
146 Nd
151 Sm
syn
90 y
β−
151 Eu
152 Sm
26.75%
-
(α)
148 Nd
153 Sm
syn
46.284 h
β−
153 Eu
154 Sm
22.75%
>2.3×1018 y
(β− β− )
154 Gd
Decay modes in parentheses are predictit, but hae nae yet been observed | references