Symbol	Th
Atomic number	90
Group	-
Period	7
Block	f
Classification	Actinide

Appearance	Silvery, often with black tarnish
Color	Silver

Number of protons	90 p+
Number of neutrons	142 n0
Number of electrons	90 e-

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.

Phase at STP	Solid
Density	11.724 g/cm3
Atomic weight	232.038 u

Melting point	2023 K 1749.85 °C 3181.73 °F
Boiling point	5061 K 4787.85 °C 8650.13 °F
Heat of vaporization	514.4 kJ/mol

Electronegativity (Pauling Scale)	1.3
Electron affinity	112.72 kJ/mol
Oxidation states	+1, +2, +3, +4 (a weakly basic oxide)
Ionization energies	587 kJ/mol 1110 kJ/mol 1930 kJ/mol 2780 kJ/mol

Electron configuration Shorthand configuration	[Rn] 6d2 7s2
Electron configuration Full configuration	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 6d2 7s2
Electron configuration chart	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 6d2 7s2
Electrons per shell	2, 8, 18, 32, 18, 10, 2
Valence electrons	2
Valency electrons	4
Bohr model	Figure: Shell diagram of Thorium (Th) atom.
Orbital Diagram 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 6s 6p 6d 7s

Discovery

Jöns Jakob Berzelius (1829)

CAS Number	7440-29-1
ChemSpider ID	22399
EC number	231-139-7
PubChem CID Number	23960