Meaning of ATOMIC NUMBER 90

WordNet Dictionary
	Definition:		[n]  a soft silvery-white tetravalent radioactive metallic element; isotope 232 is used as a power source in nuclear reactors; occurs in thorite and in monazite sands
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	Synonyms:		Th, thorium
	See Also:		metal, metallic element, monazite, radiothorium, thorite, thorium-228