Atomic number:69

Group numbers:3

Period:6

Electronic configuration:[Xe] 4f¹³ 6s²

Formal oxidation number:+3

Electronegativities:1.25

Atomic radius / pm:172.4

Relative atomic mass:168.93421 ± 0.00002

 

Thulium was discovered by Per Theodore Cleve (SE) in 1879. Named after Thule, an ancient name for Scandinavia. It is a soft, malleable, ductile, silvery metal that tarnishes in air and reacts with water. Thulium dust is flammable. Thulium is found with other rare earths in the minerals gadolinite, euxenite, xenotime and monazite. Radioactive thulium is used to power portable x-ray machines, eliminating the need for electrical equipment.

Density / g dm^-3:9321 (293 K)

Molar volume / cm³mol^-1:18.12 (293 K)

Electrical resistivity / μΩcm:79 (20 °C)

Thermal conductivity / W m^-1K^-1:16.8

Melting point / °C:1545

Boiling point / °C:1950

Heat of fusion / kJ mol^-1:18.4

Heat of vaporization / kJ mol^-1:247

Heat of atomization / kJ mol^-1:233.43

1st ionization energy / kJ mol^-1:596.70

2nd ionization energy / kJ mol^-1:1162.66

3rd ionization energy / kJ mol^-1:2284.79

in the atmosphere / ppm:-

in the Earth's crust / ppm:0.32

in the oceans / ppm:0.00000004