Symbol: Rb
Atomic Number: 37
Atomic Weight: 85.4678
Boiling Point: 961 K
Melting Point: 312.63 K
Density at 300K: 1.532 g/cm3
Covalent radius: 2.16
Atomic radius: 2.98
Atomic volume: 55.9 cm3/mol
First ionization potental: 4.177 V
Specific heat capacity: 0.363 Jg-1K-1
Thermal conductivity: 58.2 Wm-1K-1
Electrical conductivity: 47.8 106Ω-1m-1
Heat of fusion: 2.34 kJ/mol
Heat of vaporization: 69.2 kJ/mol
Electronegativity: 0.82 (Pauling's)

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(So named (Latin rubidus, "red") by its discoverers, from the red lines in its spectrum) A soft, silvery-white, very reactive, metallic chemical element, one of the alkali metals, that ignites spontaneously in air and reacts violently with water. It occurs in the minerals pollucite, carnallite, leucite, and lepidolite, from which it is obtained commercially. It is used as a catalyst, in photoelectric cells, in cathode-ray tubes, and in filaments of vacuum tubes. Similar to potassium in its chemical properties, one of rubidium's natural isotopes is radioactive and could be used to locate tumors.

Rubidium was discovered spectroscopically in 1861 in Heidelberg, Germany by Robert Wilhelm Bunsen and Gustav Kirchhoff as an impurity in samples of the mineral lepidolite.

Symbol: Rb
Atomic number: 37
Atomic weight: 85.4678
Density (at room temperature and pressure): 1.532 g/cc
Melting point: 39.31°C
Boiling point: 688°C
Main valences: +1
Ground state electron configuration: [Kr]5s1

See also: rubidium-strontium dating

Ru*bid"i*um (?), n. [NL., fr. L. rubidus red, fr. rubere to be red. So called from two dark red spectroscopic lines by means of which it was discovered in the lepidolite from Rozena, Moravia. See Rubicund.] Chem.

A rare metallic element. It occurs quite widely, but in small quantities, and always combined. It is isolated as a soft yellowish white metal, analogous to potassium in most of its properties. Symbol Rb. Atomic weight, 85.2.


© Webster 1913.

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