Rubidium
A soft, highly reactive metal used in atomic clocks.
Inside the Rubidium atom
Switch between Bohr and Quantum Cloud modes to compare a simple teaching model with a more realistic probability-based view, and follow the guided tour to explore the Rubidium atom step by step.
Electron configuration
[Kr] 5s1
A neutral Rubidium atom has 37 electrons (equal to its proton count). Choosing a different isotope above changes only the neutron count.
Shell distribution
Electrons fill inner shells before outer ones; the outermost (valence) shell drives the element's chemistry.
Physical & atomic properties
- State (room temp)
- Solid
- Melting point
- 312 K (39 °C)
- Boiling point
- 961 K (688 °C)
- Density
- 1.532 g/cm³
- Electronegativity
- 0.82 Pauling
- Atomic radius
- 235 pm
- 1st ionization energy
- 403 kJ/mol
- Category
- Alkali metals
Discovery & naming
- Discovered
- 1861
- Discovered by
- Robert Bunsen and Gustav Kirchhoff
- Origin of name
- Latin 'rubidus', meaning deep red.
Notable uses
Atomic clocks, specialty glass, and research.
Where Rubidium comes from
Several comparable sources
Both slow neutron capture in dying stars and rapid capture in explosive events contribute meaningfully.
Simplified origin map — many elements form through more than one astrophysical pathway.
Summary
- Atomic number
- 37
- Atomic mass
- 85.468
- Category
- Alkali metals
- Group · Period
- 1 · 5
- Block
- s-block
- Shells
- 2 · 8 · 18 · 8 · 1