- a nonmetallic element chemically resembling sulfur and tellurium, occurring in several allotropic forms, as crystalline and amorphous, and having an electrical resistance that varies under the influence of light. Symbol: Se; atomic weight: 78.96; atomic number: 34; specific gravity: (gray) 4.80 at 25°C, (red) 4.50 at 25°C.
Origin of selenium
Examples from the Web for selenium
He was also the person who first identified silicon, selenium, thorium, and serium.After Dominick
J. J. Berzelius
November 7, 2008
Why, mirrors and selenium are, at best, ten per cent efficient!The Big Bounce
Walter S. Tevis
It is found associated likewise with selenium and tellurium.
Selenium, indispensable in the apparatus, was discovered by Berzelius in 1817.
When selenium is rapidly cooled from a fused condition it is a non-conductor.
I must try a different solution of selenium on the metal plate.Tom Swift and his Photo Telephone
- a nonmetallic element that exists in several allotropic forms. It occurs free in volcanic areas and in sulphide ores, esp pyrite. The common form is a grey crystalline solid that is photoconductive, photovoltaic, and semiconducting: used in photocells, solar cells, and in xerography. Symbol: Se; atomic no: 34; atomic wt: 78.96; valency: –2, 4, or 6; relative density: 4.79 (grey); melting pt: 221°C (grey); boiling pt: 685°C (grey)
Word Origin and History for selenium
element name, Modern Latin, from Greek selene "moon" (see Selene). Named by Berzelius (1818), on analogy of tellurium, with which it had been at first confused, and which was named for the earth. Despite the -ium ending it is not a metal and a more appropriate name selenion has been proposed.
- A nonmetallic essential trace element used in its disulfide form as an antiseborrheic and as a radioisotope to image the pancreas and parathyroid glands. Atomic number 34.
- A nonmetallic element that occurs in a gray crystalline form, as a red powder, or as a black glassy material. It is highly photosensitive and can be used to convert light into electricity. Its ability to conduct electricity also increases with higher exposure to light. For these reasons selenium is used in photocopying technology, photography, and solar cells. Atomic number 34; atomic weight 78.96; melting point 217°C; boiling point 684.9°C; specific gravity (gray) 4.79; (red) 4.5; (black) 4.28; valence 2, 4, or 6. See Periodic Table.