The name has been derived from the Greek word ‘Selene’, the name of a Goddess of the moon. It was discovered in 1817.
There is a metallic and a non-metallic form of Selenium. Its electrical conductivity varies depending on the amount of light it receives. Hence its use in electric eyes and light meters. In electric photocopiers it is the amount of light falling on the Selenium drum that determines the amount of toner that gets attracted to the drum.
Selenium is also used in solar cells (Cadmiumselenide, CdSe), semiconductors, diodes, t.v. cameras, and as a catalyst in a.o. the manufacture of benzene.
When added to glass in small doses it makes the glass colourless, when added in large doses (25% ) it gives the glass a ruby red colour.