Atomic number:90

Group numbers:3

Period:7

Electronic configuration:[Rn] 6d² 7s²

Formal oxidation number:+4

Electronegativities:1.3

Atomic radius / pm:179.8

Relative atomic mass:232.03806 ± 0.00002

 

Thorium was discovered by Jöns Jacob Berzelius (SE) in 1828. Named after Thor, the mythological Scandinavian god of war. It is a heavy, grey, soft, malleable, ductile, radioactive metal that tarnishes in air and reacts with water. It reacts violently with oxidants. Thorium is found in various minerals like monazite and thorite. It is used in making strong alloys, in ultraviolet photoelectric cells. It is a common ingredient in high-quality lenses. When bombarded with neutrons thorium creates uranium-233, a nuclear fuel.

Density / g dm^-3:11720 (293 K)

Molar volume / cm³mol^-1:19.80 (293 K)

Electrical resistivity / μΩcm:13 (20 °C)

Thermal conductivity / W m^-1K^-1:54

Melting point / °C:1750

Boiling point / °C:4788

Heat of fusion / kJ mol^-1:19.2

Heat of vaporization / kJ mol^-1:513.67

Heat of atomization / kJ mol^-1:598.65

1st ionization energy / kJ mol^-1:608.51

2nd ionization energy / kJ mol^-1:1109.59

3rd ionization energy / kJ mol^-1:1929.72

in the atmosphere / ppm:-

in the Earth's crust / ppm:3.5

in the oceans / ppm:0.0007