| Attribute | Rubidium × | Potassium × |
|---|---|---|
| Atomic mass (u) | 85.468 | 39.0983 |
| Standard state | Solid | Solid |
| Oxidation states |
|
|
| Electron configuration | [Kr]5s¹ | [Ar]4s¹ |
| Atomic radius (van der waals) (pm) | 303 | 275 |
| Electronegativity (pauling scale) | 0.82 | 0.82 |
| Electron affinity (eV) | 0.468 | 0.501 |
| Ionization energy (eV) | 4.177 | 4.341 |
| Boiling point (K) | 961 | 1032 |
| Melting point (K) | 312.46 | 336.53 |
| Density (g/cm³) | 1.53 | 0.89 |
| Atomic number | 37 | 19 |
| Group name | Alkali metal | Alkali metal |
| Discovered (year) | 1861 | 1807 |
| Symbol | Rb | K |