Th
Thorium · element 90
Actinide · Solid at room temperature
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.
Key facts
Atomic mass
232.03774 u
how heavy one atom is
Phase (room temp.)
Solid
Density
11.724 g/cm³
how tightly packed it is
Melting point
2023 K (1750 °C)
when solid turns to liquid
Boiling point
5061 K (4788 °C)
when liquid turns to gas
Period
7
its row in the periodic table
Group
3
its column in the periodic table
Block
F-block
the neighbourhood it lives in
Electronegativity
1.3
how strongly it pulls electrons
Electron configuration
[Rn] 6d2 7s2
where its electrons live
Shells
2 · 8 · 18 · 32 · 18 · 10 · 2
electrons in each layer, inside to out
Discovered by
Jöns Jakob Berzelius
who found it
Appearance
silvery, often with black tarnish
what it looks like
Source: Wikipedia