90 - Thorium actinide
Discovered by Jöns Jakob Berzelius in 1828
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.
Periodic table
| Shell | Electrons | Orbitals |
|---|---|---|
| 1 | 2 | 2 in 1s |
| 2 | 8 | 2 in 2s + 6 in 2p |
| 3 | 18 | 2 in 3s + 6 in 3p + 10 in 3d |
| 4 | 32 | 2 in 4s + 6 in 4p + 10 in 4d + 14 in 4f |
| 5 | 18 | 2 in 5s + 6 in 5p + 10 in 5d |
| 6 | 10 | 2 in 6s + 6 in 6p + 2 in 6d |
| 7 | 2 | 2 in 7s |
Electron shells
silvery, often with black tarnish Appearance
232 u Atomic Mass
5.06k K Boiling Point
4 Group
4 Common Oxidation States
2.06 Å Covalent Radius
11.7 g/cm³ Density
113 kJ/mol Electron Affinity
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 6d2 Electron Configuration
[Rn] 6d2 7s2 Electron Configuration (semantic)
1.3 Electronegativity
90 Electrons
6.31 eV First Ionization Energy
4 ICSD Oxidation States
587, 1110, 1930, 2780 kJ/mol Ionization Energies
2.03k K Melting Point
47 Mendeleev Number
26.2 J/(mol·K) Molar Heat
7 Number of Shells
142 Neutrons
90 Atomic Number
12 Number of Isotopes
2, 3, 4 Oxidation States
7 Period
Solid Phase
90 Protons
2, 8, 18, 32, 18, 10, 2 Electron Shell Occupations
0.113 J/(g K) Specific Heat