What element has the symbol 'Th'?

The story behind the answer

The symbol Th stands for Thorium, a silvery, weakly radioactive metal in the actinide series (atomic number 90). It was discovered in 1829 by Jöns Jakob Berzelius and named after Thor, the Norse god of thunder. The other options have different symbols: Tellurium is Te, Thallium is Tl, and Tantalum is Ta.

Remember it with: “Th is for Thor’s hammer”—powerful and heavy, like this dense element. Thorium was once used in gas lamp mantles for bright white light and is being explored as a potential nuclear fuel (Th-232 can breed U-233). To avoid mix-ups: Te = Tellurium (from tellus, Earth), Tl = Thallium (green spectral line), Ta = Tantalum (from Tantalus).