Selenium (Se)

Amorphous selenium ([Ar]3d¹⁰4s²4p⁴) (CAS 7782-49-2) is either a reddish powder or a black, vitreous solid; crystalline selenium is either red or gray, depending on the crystal structure. This element resembles sulfur in its various forms and in its compounds. Selenium has many electrical properties, being both photovoltaic, where light converts to increased illumination. Below its melting point, selenium is a p-type semiconductor.