Beryllium

a steel-gray, bivalent, hard, light, metallic element, the salts of which are sweet: used chiefly in copper alloys for better fatigue endurance, in springs, and in electrical contacts. Symbol: Be; atomic weight: 9.0122; atomic number: 4; specific gravity: 1.8 at 20° C.
Historical Examples

Occult Chemistry Annie Besant and Charles W. Leadbeater
Anything You Can Do … Gordon Randall Garrett
The Last Evolution John Wood Campbell
The Great Dome on Mercury Arthur Leo Zagat
Encyclopaedia Britannica, 11th Edition, Volume 3, Slice 6 Various
Deepfreeze Robert Donald Locke
Anything You Can Do … Gordon Randall Garrett
Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 7 Various
A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Frank Bertram Wade
A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Frank Bertram Wade

noun
a corrosion-resistant toxic silvery-white metallic element that occurs chiefly in beryl and is used mainly in X-ray windows and in the manufacture of alloys. Symbol: Be; atomic no: 4; atomic wt: 9.012; valency: 2; relative density: 1.848; melting pt: 1289°C; boiling pt: 2472°C Former names glucinum, glucinium
n.
beryllium
(bə-rĭl’ē-əm)
Symbol Be
A hard, lightweight, steel-gray metallic element of the alkaline-earth group, found in various minerals, especially beryl. It has a high melting point and is corrosion-resistant. Beryllium is used to make sturdy, lightweight alloys and aerospace structural materials. It is also used as a neutron moderator in nuclear reactors. Atomic number 4; atomic weight 9.0122; melting point 1,278°C; boiling point 2,970°C; specific gravity 1.848; valence 2. See Periodic Table.