Rubidium (Rb)

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Rubidium 37Rb85.4678

Discovered in 1861 by R.W. Bunsen and G. Kirchhoff at the University of Heidelberg, Germany.

[Latin, rubidius = deepest red]

French: rubidium
Germen: Rubidium
Italian: rubidio
Spanish: rubidio

Description: Rubidium is a soft, white, metal which is silvery when first cut but it oxidises rapidly in air and ignites. It reacts violently with water. Rubidium is obtained by the reaction of calcium or potassium metal with rubidium chloride. The metal and its compounds are rarely used commercially, and only a little is used for research purposes.


Further Materials properties


Crystal structure:

(cell dimensions/pm), space group, 
b.c.c. (a=562) Im3m

X-ray diffractions mass absorption coefficients: CuKa 117 (µ/r) / cm2g-1
MoKa 90 (µ/r) / cm2g-1
Neutron scattering length: 0.709 b/10-12 cm
Thermal neutron capture cross-section: 0.38 sa / barns
Density: 1532 kg/m-3 [293 K]; 1475 [liquid at m.p.]
Melting point: 39.05°C / 312.2°K
Boiling point: 687.85°C / 961°K
Molar volume: 55.79 cm3
Thermal conductivity: 58.2 [300 K] W m-1K-1
Coefficient of linear thermal expansion: 90 x 10-6 K-1
Electrical resistivity: 12.5 x 10-8 [293 K] Ωm
Mass magnetic susceptibility: +2.49 x 10-9(s) kg-1m3
Radi: Rb+ 149; atomic 247.5; van der Waals 244
Electronegativity: 0.82 (Pauling); 0.89 (Allred); 2.34 eV (absolute)
Effective nuclear charge: 2.20 (Slater); 4.98 (Clementi); 6.66 (Froese-Fischer)
Number of Isotopes (incl. nuclear isomers): 30
Isotope mass range: 75 -> 98



Biological data


Biological role: Rubidium has no known role; its salts have a stimulatory effect.
Toxic intake: can be toxic by ingestion.
Lethal intake: LD50 (chloride, oral, mouse) = 3800 mg kg-1
Hazards: Rubidium salts are generally inert, and their toxicity is almost always that of the anion, not of the Rb+. However, in the body, rubidium substitutes for potassium and too much can be dangerous.
Level in humans
Blood: 2.49 mg dm-3
Bone: 0.1 - 5 ppm
Liver: 20 - 70 ppm
Muscle: 20 - 70 ppm
Daily dietary intake: 1.5 - 6 mg 
Total mass of element in average
[70 kg] person:

680 mg 

Geological data

 Minerals: No minerals as such are known, but rubidium is present in significant amounts in lepidolite (see lithium), pollucite(see caesium) and carnallite (see potassium).

World production: n.a.
Reserves: n.a.
Specimen: available as ingots in sealed ampoules. Danger!


Sun: 400 (relative to H = 1 x 1012)
Earth's crust: 90 ppm
Seawater 0.12 ppm
Residence time: 800 000 years
Classification: accumulating
Oxidation state: I

  Source: Emsley, J. (1998) The Elements (3rd Edition)

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Overview of elements with access to our shop

1 18
2 13 14 15 16 17
Li Be B C
Na Mg 3 4 5 6 7 8 9 10 11 12 Al Si P S
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se
Rb Sr Y Zr Nb Mo
Ru Rh Pd Ag Cd In Sn Sb Te I
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi
Ce Pr Nd
Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

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