Rubidium
Rubidium is a chemical element with symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group, with an atomic mass of 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other alkali metals, such as very rapid oxidation in air.
A stylized shell model. Electrons are quantum objects, not particles following these literal paths. Sizes and motion are illustrative.
36 is the [Kr] core total across four shells.
At a glance
- Atomic number
- 37
- Atomic mass
- 85.46783 u
- Phase
- Solid
- Density
- 1.532 g/cm³
- Melting point
- 312.45 K
- Boiling point
- 961 K
- First ionization energy
- 403 kJ/mol
- Electronegativity
- 0.82
- Electron affinity
- 46.884 kJ/mol
- Molar heat capacity
- 31.06 J/(mol·K)
- Period
- 5
- Appearance
- grey white
Conditions and isotopes affect measured properties. Some properties of short-lived elements are predicted. Electronegativity uses the Pauling scale.
Keep exploring
Explore the stories, imagery, and reference data in more depth. Properties with no value in the reference are marked unavailable.