See Also: Thorium(medicine)
thorium(dictionary)
thorium compounds(medicine)
thorium dioxide(medicine)
uranium-thorium-lead dating(encyclopedia)

thorium (iou)



thorium noun. M19.
[formed as THORITE + -IUM.]
A radioactive metallic chemical element, atomic no. 90, which is a member of the actinide series and occurs in monazite, thorite, and some other minerals. (Symbol Th.)
Comb.: thorium-lead designating a method of isotopic dating, and results obtained with it, based on the measurement of the proportions in rock of thorium-232 and its ultimate decay product, lead-208; thorium series the radioactive series of isotopes resulting from the decay of thorium-232 (the commonest natural isotope of thorium).