Potassium
Potassium is a chemical element with symbol K (derived from Neo-Latin, kalium) and atomic number 19. It was first isolated from potash, the ashes of plants, from which its name is derived. In the Periodic table, potassium is one of seven elements in column (group) 1 (alkali metals):they all have a single valence electron in their outer electron shell, which they readily give up to create an atom with a positive charge - a cation, and combine with anions to form salts.
A stylized shell model. Electrons are quantum objects, not particles following these literal paths. Sizes and motion are illustrative.
18 is the [Ar] core total across three shells.
At a glance
- Atomic number
- 19
- Atomic mass
- 39.09831 u
- Phase
- Solid
- Density
- 0.862 g/cm³
- Melting point
- 336.7 K
- Boiling point
- 1,032 K
- First ionization energy
- 418.8 kJ/mol
- Electronegativity
- 0.82
- Electron affinity
- 48.383 kJ/mol
- Molar heat capacity
- 29.6 J/(mol·K)
- Period
- 4
- Appearance
- silvery gray
Conditions and isotopes affect measured properties. Some properties of short-lived elements are predicted. Electronegativity uses the Pauling scale.
Keep exploring
Explore the stories, imagery, and reference data in more depth. Properties with no value in the reference are marked unavailable.