Erbium is a chemical element in the lanthanide series, with the symbol Er and atomic number 68. A silvery-white solid metal when artificially isolated, natural erbium is always found in chemical combination with other elements on Earth. As such, it is a rare earth element which is associated with several other rare elements in the mineral gadolinite from Ytterby in Sweden.Symbol: Er
Electron configuration: Xe 4f12 6s2
Discovered: 1843
Melting point: 1,529 °C
Atomic number: 68
Atomic mass: 167.259 ± 0.003 u