Terbium

Chemical element with atomic number 65 (Tb)

Terbium is a chemical element; it has symbol Tb and atomic number 65. It is a silvery-white, rare earth metal that is malleable and ductile. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with water, evolving hydrogen gas.

From Wikipedia, under CC BY-SA. More on occurri.