Potassium (K)
Potassium (K) is element 19, an alkali metal. Atomic mass 39.0983, configuration [Ar] 4s¹. Properties, isotopes, oxidation states, uses and history, with an interactive 3D atom model.
Key facts
| Atomic number | 19 |
|---|---|
| Symbol | K |
| Standard atomic weight | 39.0983(1) |
| Category | Alkali Metal |
| Group | 1 |
| Period | 4 |
| State at room temperature | Solid |
| Electron configuration | [Ar] 4s¹ |
| Valence electrons | 1 |
| Common oxidation states | +1 |
| Common ions | K⁺ |
| Electronegativity (Pauling) | 0.82 |
| First ionization energy | 419 kJ/mol |
| Electron affinity | 48.38 kJ/mol |
| Atomic radius | 243 pm |
| Density | 0.89 g/cm³ |
| Melting point | 63.69°C |
| Boiling point | 759°C |
| Specific heat | 0.757 J/(g·°C) |
Natural isotopes
- K-39: Stable (93.26%)
- K-40: Radioactive (0.012%)
- K-41: Stable (6.73%)
Common uses
- Fertilizers
- Soaps
- Gunpowder (KNO₃)
Where it matters
- Agriculture (NPK Fertilizers)
- Geology (K-Ar dating)
- Biology (Nerve transmission)
Hazards
- Reacts violently with water
History
| Discovered | 1807 |
|---|---|
| Discovered by | Humphry Davy |
| Name | Humphry Davy (from 'Potash') |