Images
Formula: Th
Actinide metal
Thorium is not found free in nature but is found in a number of minerals, mainly
monazite and bastnäsite. It
has 28 isotopes whose half-lives are known, and all of them are radioactive, although the most stable isotope has
a very long half-life, so it is only slightly radioactive.
It is dimorphic, changing from face centered cubic to body centered cubic above oC
(ChC).
Specific gravity: 11.7
Colour: Silvery
Melting point: 1750oC
Boiling point: 4790oC
Thorium has the largest liquid range of any element, spanning over 3000 degrees between its melting point and its
boiling point
(ChC).
Abundance in the Earth's crust: 6 parts per million by mass, 0.5 parts per million by moles
(ChC).
Abundance in the Solar System: 0.3 parts per billion by mass, 2 parts per trillion by moles
(ChC).
In compounds thorium has oxidation number 4, ie Th4+
Thorium-bearing minerals include:
Oxides
aeschynite-(Ce)
aeschynite-(Y)
euxenite-(Y)
thorianite
Phosphates
cheralite
eylettersite
Nesosilicates
britholite-(Ce)
huttonite
thorite
vicanite-(Ce)
Phyllosilicates
ekanite
Cyclosilicates
steacyite
Unclassified Silicates
umbozerite
Back to Minerals