037Alkali metal · Group 1 · Period 5
Rubidium
Rubidium (Rb) is element 37, a alkali metal in the s-block — group 1, period 5. It is a solid at room temperature with 5 electron shells (2, 8, 18, 8, 1) and an atomic mass of 85.46783 u.
- Atomic mass
- 85.47 u
- Phase · STP
- solid
- Melting
- 312 K · 39 °C
- Boiling
- 961 K · 688 °C
- Electronegativity
- 0.82
- Density
- 1.532 g/cm³
Photograph — Dnn87, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons
Identity
- Atomic number
- 37
- Standard atomic weight
- 85.47 u
- Category
- Alkali metal
- Group
- 1 · Alkali metals
- Period
- 5
- Block
- s-block
- Oxidation states
- +1
Physical properties
- Melting point
- 312 K · 39 °C
- Boiling point
- 961 K · 688 °C
- Density
- 1.532 g/cm³
- Molar heat capacity
- 31.06 J/(mol·K)
- Atomic radius
- 303 pm
- Electron affinity
- 46.884 kJ/mol
Atomic structure
37protons
48neutrons
37electrons
1valence e⁻
- Noble-gas notation
- [Kr] 5s1
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1
- Electrons per shell
- 2, 8, 18, 8, 1
Periodic trends
Where Rubidium ranks across all 118 elements.
Ionization energies
Energy to remove each successive electron (kJ/mol).
4031
2.6k2
3.9k3
5.1k4
6.8k5
8.1k6
9.6k7
13.1k8
14.5k9
26.7k10
Successive ionization energies (kJ/mol, log scale).
Discovery
- Discovered
- 1861
- Discovered by
- Robert Bunsen
- Named by
- —
- Appearance
- grey white