Rubidium – Properties and Applications

Chemical Formula


Topics Covered

Basic Information
Production of Rubidium
Health Aspects
Key Properties


Robert Bunsen and Gustav Kirchhoff discovered the element Rubidium in 1861 with the help of a spectroscope while analyzing a mineral called lepidolite. When the mineral was heated, Bunsen and Kirchhoff found deep red spectral lines from which the rubidium metal was isolated. The name, rubidium was derived from the word rubidus, which means the deepest red.

Basic Information

Name Rubidium
Symbol Rb
Atomic number 37
Atomic weight 85.4678 (3) amu
Standard state solid at 298 K
CAS Registry ID 7440-17-7
Group in periodic table 1
Group name Alkali metal
Period in periodic table 5
Block in periodic table s-block
Color silvery white
Classification Metallic
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/cm3
Phase at Room Temperature Solid


Significant amounts of rubidium are present in the minerals such as Lepidolite, Pollucite and Carnallite. Traces of rubidium are also present in the minerals such as Leucite and Zinnwaldite. The metal is also found in mineral springs and seawater. Rubidium is an abundant element at around 35 to 75 ppm.


Rubidium has two naturally occurring isotopes Rubidium-85 and Rubidium-87. Rubidium-87 is a radioactive isotope is used to determine the age of old rocks. It has a half-life of 49 billion years. It is also used as a frequency standard in high-accuracy timing equipment such as GPS receivers. It is also used to produce Bose-Einstein condensates and in laser cooling.

Production of Rubidium

Rubidium is generally produced as a by-product of lithium refining from Lepidolite. In such cases, rubidium chloride is reduced using saodium or calcium.

Health Aspects

Certain health effects of rubidium are listed below:

  • It is moderately toxic by ingestion
  • If itt ignites, it will cause thermal burns
  • Overexposurecan result in skin and eye burns
  • Failure to gain weight, hyper irritation, ataxia, skin ulcers and nervousness may occur due to over exposure

Key Properties

The key properties of rubidium are:

  • It is the second most electropositive metal
  • It is soft and silvery
  • It is highly inflammable
  • It is mildly radioactive
  • It ignites spontaneously in air
  • It vigorously reacts with water and combines with the halogens


The applications of rubidium are listed below:

  • Rubidium is mainly used to make atomic clocks. These clocks are used only when high-precision time keeping is required.
  • Rubidium is also used in the manufacture of photocells. A photocell converts light energy to electrical energy.
  • Rubidium is ideal for monitoring ischemia, a condition where blood flow is obstructed through the main coronary arteries.


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