Thorium is the chemical element with atomic number 90 and symbol . It is a actinide. It has no stable isotopes, but thorium-232 is sufficiently long-lived to occur naturally. The oxidation state is characteristic of its chemistry, distinguishing it from the more usual chemistry of many neighboring f-block elements.[ref]
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Thorium is a radioactive chemical element with the symbol Th and atomic number 90. It is a silvery-white metal that is moderately hard and malleable. Thorium is found in nature mainly in the mineral monazite, and it is considered to be a potential alternative to uranium as a nuclear fuel for nuclear reactors.