Loading your view…

periodicity.
Mass calculator
Periodic table
Period 7Actinides
90Solid
Th 232.038 Atomic mass · u
Actinides

Thorium

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.

Discovery 1828 (Jöns Jakob Berzelius)
Thorium electron shellsTh90 protons
K2L8M18N32O18P10Q2
A simplified shell model. Electron positions are illustrative.

Physical properties

Values for the element in its standard state.

Density
11.724g/cm³
Melting point
2,023K
Boiling point
5,093K
Atomic radius
Not available
Bonding type
Metallic
Molar heat
26.23J/(mol·K)

Inside the atom

Electron arrangement and the energy behind its behavior.

Full electron configuration

1s, 2 electrons; 2s, 2 electrons; 2p, 6 electrons; 3s, 2 electrons; 3p, 6 electrons; 3d, 10 electrons; 4s, 2 electrons; 4p, 6 electrons; 4d, 10 electrons; 5s, 2 electrons; 5p, 6 electrons; 4f, 14 electrons; 5d, 10 electrons; 6s, 2 electrons; 6p, 6 electrons; 6d, 2 electrons; 7s, 2 electrons;

[Rn] represents 86 core electrons. The full view shows them explicitly.

90 electrons Orbital order preserved from source

Electronegativity
1.3Pauling scale
First ionization energy
587kJ/mol
Electron affinity
Not available
Van der Waals radius
Not available
Th ThoriumAtomic number 90
587kJ/mol
Ionization energy by atomic number
Atomic numberGaps indicate unavailable data

About thorium

Appearance
Silvery, often with black tarnish
Discovery
1828 (Jöns Jakob Berzelius)

A missing value means it is unavailable in this reference dataset. Values can vary with measurement method and conditions.