Erbium is a chemical element that originated from Ytterby, Sweden. It was first mentioned in 1842 and observed by G. Mosander. “Er” is the canonical chemical symbol of erbium. Its atomic number in the periodic table of elements is 68 with a location at Period 6 and Group 3, belonging to the f-block. The relative atomic mass of erbium is 167.259(3) Dalton, the number in the brackets indicating the uncertainty.