About the element

Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic.


Key facts

  • Symbol: Se
  • Atomic number: 34
  • Atomic mass: 78.96 u


Most of the targeted by-products elements are Critical Raw Materials (CRMs). CRMs combine raw materials of high importance to the EU economy and of high risk associated with their supply.

Selenium is not part of the EU 2020 Critical Raw Materials List. Its criticality is considered to be high.

Main uses of Selenium

Metallurgy: Selenium is used in alloys to replace more toxic lead, to improve the machinability of steel and of copper alloys, and in the production of electrolytic manganese.

Glass production: Selenium is used as to remove the green tint caused by iron impurities, to produce a red colour, and to reduce solar heat transmission through glass.

And also… in electronics (in rectifiers, in voltage surge protection devices, and in photovoltaic solar cells), in agricultural& biological products, such as food additives and fertilisers, in pigments, in lithium–selenium batteries, etc.