selenium

[ si-lee-nee-uhm ]

noun

, Chemistry.

1. 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. : Se; : 78.96; : 34; : (gray) 4.80 at 25°C, (red) 4.50 at 25°C.

selenium

/ sɪˈliːnɪəm /

noun

1. 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)

selenium

/ sĭ-lē′nē-əm /

1. 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.
2. See Periodic Table

Word History and Origins

Origin of selenium¹

< New Latin (1818) < Greek selḗn ( ē ) moon + New Latin -ium -ium; named in allusion to its similarity to tellurium

Word History and Origins

Origin of selenium¹

C19: from New Latin, from Greek selēnē moon; named by analogy to tellurium (from Latin tellus earth)

Example Sentences

The Selenium browser that ran for seven days, for example, clicked on more than 900 Google ads, and almost 1,200 ads in all.

From MIT Technology Review

“This proposed settlement will hold the company to account for its selenium pollution and helps fund an environmental project that benefits the Tug River,” said Karan Ireland, the West Virginia Sierra Club’s senior campaign representative.

From ProPublica

He was also the person who first identified silicon, selenium, thorium, and serium.

From The Daily Beast

(a) Organic selenium compounds were reviewed and their properties examined critically with those of allied compounds.

From Project Gutenberg

(d) Two series of azo dyes of selenium have been prepared and have been shown to possess a marked tinctorial value.

From Project Gutenberg

Since Berzelius published the first resume of the chemistry of selenium, in 1818, many articles have appeared in this field.

From Project Gutenberg

No attempt has ever been made to compile a bibliography of selenium organic compounds.

From Project Gutenberg

The general conception of selenium is that it is a comparatively rare element.

From Project Gutenberg