37
Rb
Rubidium
85.4678
Rubidium (Rb)
Alkali MetalGroup 1Period 5s-block-block
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.
Latin name: Rubidium
Atomic Number
37
Atomic Mass
85.4678 g/mol
Phase (STP)
Solid
Electron Config.
[Kr] 5s¹
General
SymbolRb
Atomic Number37
Atomic Mass85.4678 g/mol
CategoryAlkali Metal
Group1
Period5
Blocks-block
Electron Configuration[Kr] 5s¹
Valence Electrons1
Coloursilvery-white metallic
Appearancegrey white
CAS NumberCAS7440-17-7
Physical Properties
Phase (STP)Solid
Density1.532 g/cm³
Melting Point39.31°C · 102.76°F · 312.46 K
Boiling Point687.85°C · 1270.13°F · 961.00 K
Atomic Properties
Atomic Radius265 pm
Electronegativity0.82 Pauling
Ionization Energy403 kJ/mol
Oxidation States+1
Ion ChargeRb+
Thermodynamic
Molar Heat31.06 J/(mol·K)
Crystal Structure
Crystal Structurebody-centered cubic
Mechanical Properties
Mohs Hardness0.3
Abundance
In Earth's Crust0.0900%
Discovery & History
Discovery Year1861
Discovered ByRobert Bunsen, Gustav Kirchhoff
Country of DiscoveryGermany
Isotopes of Rubidium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Rb-85 | 72.17% | Stable | — |
| Rb-87 | 27.83% | 4.97 × 10¹⁰ years | β⁻ |