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Thorium (Th)

From Wikipedia, the free encyclopediaThorium is a chemical element with symbol Th and atomic number 90. A radioactive actinide metal, thorium is one of only two significantly radioactive elements that still occur naturally in large quantities as a primordial element (the other being uranium). It was discovered in 1828 by the Norwegian Reverend and amateur mineralogist Morten Thrane Esmark and identified by the Swedish chemist Jöns Jakob Berzelius, who named it after Thor, the Norse god of thunder.

Thorium in the periodic table

Atomic number90
Element categoryActinide

Physical properties

Phase at STPSolid
Density11.724 g/cm3
Atomic weight232.038 u
Melting point2023 K
1749.85 °C
3181.73 °F
Boiling point5061 K
4787.85 °C
8650.13 °F

Atomic properties

Electronegativity (Pauling Scale)1.3
Electron affinity112.72 kJ/mol
Oxidation states+1, +2, +3, +4
(a weakly basic oxide)
Ionization energies
1587 kJ/mol
2 1110 kJ/mol
3 1930 kJ/mol
4 2780 kJ/mol

Electron configuration

Elektronkonfiguration (shorthand)[Rn] 6d2 7s2
Electron configuration1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 6d2 7s2
Electrons per shell2, 8, 18, 32, 18, 10, 2


Discovered byJöns Jakob Berzelius
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