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n. Symbol Rb
A soft silvery-white metallic element of the alkali group that ignites spontaneously in air and reacts violently with water, used in photocells and as a getter in the manufacture of vacuum tubes. Atomic number 37; atomic weight 85.47; melting point 39.30°C; boiling point 688°C; specific gravity (solid) 1.532; valence 1, 2, 3, 4. See Periodic Table.
(Elements & Compounds) a soft highly reactive radioactive element of the alkali metal group; the 16th most abundant element in the earth's crust (310 parts per million), occurring principally in pollucite, carnallite, and lepidolite. It is used in electronic valves, photocells, and special glass. Symbol: Rb; atomic no: 37; atomic wt: 85.4678; half-life of 87Rb: 5 × 1011 years; valency: 1, 2, 3, or 4; relative density: 1.532 (solid), 1.475 (liquid); melting pt: 39.48°C; boiling pt: 688°C
[C19: from New Latin, from Latin rubidus dark red, with reference to the two red lines in its spectrum]
ru•bid•i•um(ruˈbɪd i əm)
a silver-white, metallic, active element resembling potassium, used in photoelectric cells and radio vacuum tubes. Symbol: Rb; at. wt.: 85.47; at. no.: 37; sp. gr.: 1.53 at 20°C.
[< German (1861), = Latin rūbid(us) red (in allusion to the two red lines in its spectrum) + -ium -ium2]
Symbol Rb A soft, silvery-white element that is an alkali metal. It ignites spontaneously in air and reacts violently with water. Rubidium is used in photoelectric cells and in making vacuum tubes. Atomic number 37. See Periodic Table.
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|Noun||1.||rubidium - a soft silvery metallic element of the alkali metal group; burns in air and reacts violently in water; occurs in carnallite and lepidolite and pollucite|
metal, metallic element - any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.
carnallite - a white or reddish mineral consisting of hydrous chlorides of potassium and magnesium; used as a fertilizer and as a source of potassium and magnesium
lepidolite - a mineral of the mica group; an important source of lithium
pollucite - a rare mineral that is an important source of cesium