Properties

Atomic Number	68
CAS Registry Number	7440-52-0
Chemical Symbol	Er

History

The atomic number is 68 and the chemical symbol is Er. The name derives from the Swedish town of Ytterby (about 3 miles from Stockholm) where the ore gadolinite (in which it was found) was first mined. It was discovered by the Swedish surgeon and chemist Carl-Gustav Mosander in 1843 in an yttrium sample. He separated the yttrium into: yttrium a rose colored salt he called terbium and a deep yellow peroxide that he called erbium. In 1860 an analysis of yttrium by the German chemist Berlin found only the yttrium and the rose colored salt which was now called erbium not terbium. All subsequent workers followed Berlin in designating the rose colored rare earth as erbium.

Holden, Norman E., (2004). History of the origin of the chemical elements and their discoverers. National Nuclear Data Center. Retrieved from http://www.nndc.bnl.gov/content/elements.html