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It's Elemental

The Element Rubidium

[Click for Isotope Data]


37 Rb Rubidium 85.4678

Atomic Number: 37

Atomic Weight: 85.4678

Melting Point: 312.46 K (39.31°C or 102.76°F)

Boiling Point: 961 K (688°C or 1270°F)

Density: 1.53 grams per cubic centimeter

Phase at Room Temperature: Solid

Element Classification: Metal

Period Number: 5

Group Number: 1

Group Name: Alkali Metal

What's in a name? From the Latin word for deepest red, rubidus.

Say what? Rubidium is pronounced as roo-BID-ee-em.

History and Uses:

Rubidium was discovered by the German chemists Robert Bunsen and Gustav Kirchhoff in 1861 while analyzing samples of the mineral lepidolite (KLi2Al(Al, Si)3O10(F, OH)2) with a device called a spectroscope. The sample produced a set of deep red spectral lines they had never seen before. Bunsen was eventually able to isolate samples of rubidium metal. Today, most rubidium is obtained as a byproduct of refining lithium.

Rubidium is used in vacuum tubes as a getter, a material that combines with and removes trace gases from vacuum tubes. It is also used in the manufacture of photocells and in special glasses. Since it is easily ionized, it might be used as a propellant in ion engines on spacecraft. Recent discoveries of large deposits of rubidium suggest that its usefulness will increase as its properties become better understood.

Rubidium forms a large number of compounds, although none of them has any significant commercial application. Some of the common rubidium compounds are: rubidium chloride (RbCl), rubidium monoxide (Rb2O) and rubidium copper sulfate Rb2SO4·CuSO4·6H20). A compound of rubidium, silver and iodine, RbAg4I5, has interesting electrical characteristics and might be useful in thin film batteries.

Estimated Crustal Abundance: 9.0×101 milligrams per kilogram

Estimated Oceanic Abundance: 1.2×10-1 milligrams per liter

Number of Stable Isotopes: 1 (View all isotope data)

Ionization Energy: 4.177 eV

Oxidation States: +1

Electron Shell Configuration:


2s2   2p6

3s2   3p6   3d10

4s2   4p6


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For questions about this page, please contact Steve Gagnon.