Erbium is a chemical element, having the chemical symbol Er. Its atomic number (the number of protons) is 68. It has a standard atomic weight of 167.259 g•mol −1 and is a solid in its elemental form.
Erbium is considered a member of the "Lanthanide" class of elements. At a pressure of 101.325 kPa, it has a boiling point of 2,868 °C and a melting point of 1,529 °C.