Rubidium (Rb)
Rubidium (Rb) is element 37, an alkali metal. Atomic mass 85.4678, configuration [Kr] 5s¹. Properties, isotopes, oxidation states, uses and history, with an interactive 3D atom model.
Key facts
| Atomic number | 37 |
|---|---|
| Symbol | Rb |
| Standard atomic weight | 85.4678(3) |
| Category | Alkali Metal |
| Group | 1 |
| Period | 5 |
| State at room temperature | Solid |
| Electron configuration | [Kr] 5s¹ |
| Valence electrons | 1 |
| Common oxidation states | +1 |
| Common ions | No common ions |
| Electronegativity (Pauling) | 0.82 |
| First ionization energy | 403 kJ/mol |
| Electron affinity | 46.88 kJ/mol |
| Atomic radius | 265 pm |
| Density | 1.53 g/cm³ |
| Melting point | 39.31°C |
| Boiling point | 688°C |
| Specific heat | 0.363 J/(g·°C) |
Natural isotopes
- Rb-85: Stable
- Rb-87: Radioactive
Common uses
- Vacuum tube getters
- Photocells
- Atomic clocks
Where it matters
- Geochronology (Dating of rocks/minerals)
- Atomic clocks
Hazards
- Reacts violently with water (ignites spontaneously)
History
| Discovered | 1861 |
|---|---|
| Discovered by | Robert Bunsen & Gustav Kirchhoff |
| Name | From Latin rubidius (deep red, from spectrum) |