Potassium (K)

Alkali metals · Period 4 · Solid

Explore potassium isotopes Locate in periodic table

Element identity

Atomic number (Z): 19
Symbol: K
Atomic weight / isotope mass number: 39.0983(1)
Category: Alkali metals
Physical state (reference): Solid
Period: 4
Group (reference): 1
Block: s

Physical properties

Appearance: Silvery gray
Density: 0.862 g·cm⁻³
Melting point: 336.7 K / 63.5 °C / 146.3 °F
Boiling point: 1032 K / 759 °C / 1398 °F
Sublimation point: Not available

Atomic and material properties

Electron configuration: [Ar] 4s¹
Electrons per shell: K2 L8 M8 N1
Oxidation states: 1, −1
Electronegativity (Pauling): 0.82
Atomic radius: 243 pm
Covalent radius: 203±12 pm
Molar ionization energies: 1st: 418.8 kJ·mol⁻¹ 2nd: 3052 kJ·mol⁻¹ 3rd: 4420 kJ·mol⁻¹ 4th: 5877 kJ·mol⁻¹ 5th: 7975 kJ·mol⁻¹ 6th: 9590 kJ·mol⁻¹ 7th: 11,343 kJ·mol⁻¹ 8th: 14,944 kJ·mol⁻¹ 9th: 16,963.7 kJ·mol⁻¹ 10th: 48,610 kJ·mol⁻¹ 11th: 54,490 kJ·mol⁻¹ 12th: 60,730 kJ·mol⁻¹ 13th: 68,950 kJ·mol⁻¹ 14th: 75,900 kJ·mol⁻¹ 15th: 83,080 kJ·mol⁻¹ 16th: 93,400 kJ·mol⁻¹ 17th: 99,710 kJ·mol⁻¹ 18th: 444,880 kJ·mol⁻¹ 19th: 476,063 kJ·mol⁻¹
Thermal conductivity: 102.5 W·m⁻¹·K⁻¹
Molar heat capacity: 29.6 J·mol⁻¹·K⁻¹
Crystal structure: Body-centered cubic
CAS number: 7440-09-7

Property source: Wikipedia — Potassium, adapted from the Nuclides App snapshot. Quoted conditions and qualifiers are retained.

Sources and interpretation

Snapshot exported 24 October 2026 from the element assets used by Nuclides. Properties are a reference compilation, not a new evaluation. Missing values are shown as “Not available”. Density and phase depend on temperature, pressure and allotrope; retained conditions are part of the quoted property.

Atomic weight is dimensionless. Parentheses give uncertainty in the last quoted digits. A single integer in square brackets is an isotope mass number, not a standard atomic weight. The snapshot can differ from current evaluations; consult CIAAW standard atomic weights and the IUPAC periodic table for current values and conventions.

Element properties in the App snapshot are adapted from Wikipedia. Each element page links to its source article; text adaptations are available under CC BY-SA 4.0. No third-party images are included.

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