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Rubidium ( Rb )

Material Information

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General Description:  

Discovered in 1861 by R.W. Bunsen and G. Kirchoff in Heidelberg, Germany.

Rubidium is a soft and highly reactive member of the alkali group of metals. It is widely distributed throughout nature, but only occurs in small amounts (its abundance in the earth's crust is 310 ppm), the main source being carnallite, the hydrated chloride of magnesium and potassium. The metal is obtained by the electrolysis of the fused halide, although it can be obtained on a laboratory scale by heating the chloride with calcium metal and distilling out the metal. The metal ignites spontaneously in air and reacts violently with water and applications are limited.
   

Atomic Properties

Atomic number 37
Atomic radius - Goldschmidt ( nm ) 0.251
Atomic weight ( amu ) 85.4678
Crystal structure Body centred cubic
Electronic structure Kr 5s1
Ionization potential No. eV
1 4.18
2 27.3
3 40.0
4 52.6
5 71.0
6 84.4
Natural isotope distribution Mass No. %
85 72.17
87 27.83
Photo-electric work function ( eV ) 2.1
Thermal neutron absorption cross-section ( Barns ) 0.5
Valences shown 1, 2, 3, 4

Electrical Properties

Electrical resistivity @20C ( µOhmcm ) 12.1
Temperature coefficient @0-100C ( K-1 ) 0.0048

Mechanical Properties

Material condition Polycrystalline
Bulk modulus ( GPa ) 2.5
Hardness - Mohs 0.3
Poisson's ratio 0.30
Tensile modulus ( GPa ) 2.35

Physical Properties

Boiling point ( C ) 686
Density @20C ( g cm-3 ) 1.532
Melting point ( C ) 38.89

Thermal Properties

Coefficient of thermal expansion @0-100C ( x10-6 K-1 ) 9.0
Latent heat of evaporation ( J g-1 ) 887
Latent heat of fusion ( J g-1 ) 25.7
Specific heat @25C ( J K-1 kg-1 ) 360
Thermal conductivity @0-100C ( W m-1 K-1 ) 58.2
All information and technical data are given as a guide only. Although every effort has been made to ensure that the information is correct, no warranty is given as to its completeness or accuracy.

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