90Th232.038

Thorium

Actinide

Thorium 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.

Phase: SolidAppearance: silvery, often with black tarnish

2, 8, 18, 32, 18, 10, 2

Physical Properties

Atomic Mass232.03774 u

Density11.724 g/cm³

Melting Point2023 K

Boiling Point5061 K

Molar Heat26.23 J/(mol·K)

Period7

PhaseSolid

Chemical Properties

Electron Configuration1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 6d2

Semantic Config[Rn] 6d2 7s2

Shells2, 8, 18, 32, 18, 10, 2

Electron Affinity112.72 kJ/mol

Electronegativity1.3

Ionization Energies

IE1: 587 kJ/molIE2: 1110 kJ/molIE3: 1930 kJ/molIE4: 2780 kJ/mol

Discovery

Discovered byJöns Jakob Berzelius

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