Erbium is a chemical element. Its ground state electronic configuration is [Xe]4f12 6s2. Natural erbium is a mixture of six stable isotopes. Monazite and xenotime are the principal erbium ores, in which erbium occurs together with other members of the rare earth elements, or the lanthanides. It can be separated from the other rare earths by ion exchange or solvent extraction techniques. The discovery of erbium is attributed to Carl G. Mosander(1842). Its name is derived from Ytterby, a small town in Sweden, where the first rare earth mineral (gadolinite) had been found. The elements ytterbium, yttrium, and terbium have also been named after the town of Ytterby.
Pure erbium metal was first prepared in 1934. It is a silver-white, malleable, and ductile metal. The metal is not oxidized as rapidly as other rare earth metals when exposed to air. Erbium chemistry is dominated by the trivalent erbium (III) ion, Er3+. Its chemical behavior resembles that of yttrium and the heavy rare earth elements. The ground state electronic configuration of Er3+ is [Xe]4f13. Because of erbium's narrow absorption band in the green region of visible light (at wavelengths of ca. 530 nanometers, or 2.09 × 10-5 inches), erbium (III) salts are pink. Due to the high chemical stability of trivalent erbium, erbium (III) oxide is used to color glassware pink. Erbium is of importance to the technology of optical amplification in glass fibers. Erbium-doped crystals can be used to generate laser beams having wavelengths in the vicinity of 2,900 nanometers (1.14 ×10-4 inches). Such lasers are being used in laser surgery. The laser beam is strongly absorbed by water, so that the energy in hitting its target is confined to the surface layer of tissue. Phosphors based on erbium can convert infrared light to visible light (upconversion).