Terbium is a chemical element with the symbol Tb and atomic number 65. It is a silvery-white rare earth metal that is malleable, ductile and soft enough to be cut with a knife. Terbium is never found in nature as a free element, but it is contained in many minerals, including cerite, gadolinite, monazite, xenotime and euxenite.Symbol: Tb
Electron configuration: Xe 4f9 6s2
Melting point: 1,356 °C
Atomic number: 65
Discovered: 1843
Atomic mass: 158.92535 ± 0.00002 u