Thulium
Atomic number 69
Group, block group n/a, f-block
Period period 6
Element category lanthanide
Standard atomic weight (±) (Ar) 168.93422(2)1
Electron configuration Xe 4f13 6s2
per
shell
2, 8, 18, 31, 8, 2
Physical properties
Phase solid
Melting point 1818 K (1545 °C, 2813 °F)
Boiling point 2223 K (1950 °C, 3542 °F)
Density near r.
t. 9.32 g/cm3
when liquid, at m.p. 8.56 g/cm3
Heat of fusion 16.84 kJ/mol
Heat of vaporization 191 kJ/mol
Molar heat capacity 27.03 J/(mol·K)
vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at
T (K) 1117 1235 1381 1570 (1821) (2217)
Atomic properties
Oxidation states 2, 3 (a basic oxide)
Electronegativity Pauling scale: 1.25
Ionization energies 1st: 596.7 kJ/mol
2nd: 1160 kJ/mol
3rd: 2285 kJ/mol
Atomic radius empirical: 176 pm
Covalent radius 190±10 pm
Miscellanea
Crystal structure hexagonal close-packed (hcp) Hexagonal close packed crystal structure for thulium
Thermal expansion poly: 13.3 µm/(m·K) (at r.
t.)
Thermal conductivity 16.9 W/(m·K)
Electrical resistivity poly: 676 nΩ·m (at r.
t.)
Magnetic ordering paramagnetic (at
300 K)
Young's modulus 74.
0 GPa
Shear modulus 30.5 GPa
Bulk modulus 44.5 GPa
Poisson
ratio 0.213
Vickers hardness 470–650 MPa
Brinell hardness 470–900 MPa
CAS Number 7440-30-4
History
Naming after Thule, a mythical region in Scandinavia
Discovery and first isolation Per Teodor Cleve (1879)