thorium -
A chemical element symbol Th with atomic number 90.
Wikipedia
Thorium is a chemical element with the symbol Th and atomic number 90. Thorium is a naturally occurring, slightly radioactive metal. A Thorium atom has 90 protons and 90 electrons, of which 4 are valence electrons.
OmegaWiki Dictionary
Ω
thorium Chemical element with symbol Th and atomic number 90. It is a silvery white actinide.
