Thorium was discovered by Jöns Jacob Berzelius, a Swedish chemist, in 1828.
Name: Thorium
Symbol: Th
Atomic number: 90
Atomic weight: 232.04
State: solid
Group, period, block: n/a, 7, f
Color: silvery, often with black tarnish
Classification: actinide
Electron configuration: 6d2 7s2
2,8,18,32,18,10,2
Physical properties
Density: 11.7 g/cm-3
Melting point: 2115 K,1842 °C,3348 °F
Boiling point: 5061 K,4788 °C,8650 °F
Atomic properties
Oxidation states: 4, 3, 2, 1
Electronegativity: 1.3 (Pauling scale)
Ionization energies: 1st: 587 kJ·mol-1
Covalent radius: 206±6 pm
Van der Waals radius: no data
- Th
Electron Configuration
Isotopes
Thorium has six naturally occurring isotopes, none of these isotopes are stable. However, one isotope, 232Th, is relatively stable, with a half-life of 14.05 billion years. Thirty radioisotopes of Thorium have been characterized. The known isotopes of thorium range in mass number from 209 to 238.