Periodic Table of Elements




Rubidium was discovered in 1861 by German chemists Robert Bunsen (1811-99) and Gustav Kirchhoff (1824-87), in the mineral lepidolite through the use of a spectroscope.

Name: Rubidium
Symbol: Rb
Atomic number: 37
Atomic weight: 85.468
State: solid
Group, period, block: 1, 5, s
Color: grey white
Classification: alkali metal
Electron configuration: 5s1

Physical properties

Density: 1.532 g/cm-3
Melting point: 312.46 K,39.31 C,102.76 F
Boiling point: 961 K,688 C,1270 F

Atomic properties

Oxidation states: 1
Electronegativity: 0.82 (Pauling scale)
Ionization energies: 1st: 403 kJmol-1
Covalent radius: 2209 pm
Van der Waals radius: 303 pm
  • Rb
  • Electron Configuration


There are two naturally occurring isotopes of rubidium exist, 85Rb, and 87Rb.