出典:Wikipedia
出典:『Wikipedia』 (2011/07/26 10:10 UTC 版)
Thorium ( /ˈθɔriəm/ thohr-ee-əm) is a naturally occurring radioactive chemical element, found in abundance throughout the world. Thorium atoms (symbol Th) have an atomic number of 90, with 90 protons and 90 electrons, of which 4 are valence electrons. It was discovered in 1828 and named after Thor, the Norse god of thunder.
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