Periodic table / Alkali metals
19Potassium
Potassium is an alkali metal in group 1, period 4. At 25 °C it is a solid.
- Symbol
- K
- Atomic number
- 19 protons in the nucleus
- Standard atomic weight
- 39.098 ± 0.001
- Electron configuration
- [Ar] 4s1
- Electrons in each shell
- 2, 8, 8, 1
- Group, period, block
- 1, 4, s
- Family
- Alkali metals
- State at 25 °C
- solid
- Electronegativity
- 0.82 (Pauling scale)
- First ionisation energy
- 418.8 kJ/mol (4.34066373 eV)
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Where these numbers come from
Atomic weight: IUPAC CIAAW, abridged standard atomic weights 2024. Electron configuration and ionisation energy: NIST Atomic Spectra Database. Family, state and electronegativity: PubChem. See Sources. Melting points, boiling points and densities are left out for now: published values differ between sources, and we will add them once each has been checked.