1939.098KPotassium
Potassium (K) — element 19alkali metal · group 1, period 4
Potassium is a chemical element with the symbol K and atomic number 19. It is an alkali metal in group 1, period 4 of the periodic table (the s-block), with a standard atomic mass of 39.098 u. At room temperature (25 °C) potassium is a solid.
💡 Known for: A vital electrolyte for nerves and muscles; potash fertilisers are rich in it and bananas are a well-known dietary source.
# Potassium properties
| Symbol | K |
|---|---|
| Atomic number | 19 |
| Atomic mass | 39.098 u |
| Category | alkali metal |
| Group | 1 |
| Period | 4 |
| Block | s-block |
| Electron configuration | [Ar] 4s¹ |
| Full configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ |
| Electrons per shell | 2, 8, 8, 1 |
| Protons / electrons | 19 / 19 |
| State at 25 °C | solid |
| Melting point | 336.53 K (63.4 °C, 146.1 °F) |
| Boiling point | 1032 K (758.9 °C, 1397.9 °F) |
| Density | 0.862 g/cm³ |
| Electronegativity (Pauling) | 0.82 |
| First ionization energy | 4.341 eV |
| Atomic radius | 243 pm |
| Discovered | 1807 |
# Electron configuration of potassium
The electron configuration of potassium is [Ar] 4s¹, written out in full as 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹. Its 19 electrons fill 4 shells as 2, 8, 8, 1, so the outermost shell holds 1 electron. As a group 1 element, potassium has 1 valence electron.
# Related elements
ArArgonprevious elementCaCalciumnext elementHHydrogengroup 1LiLithiumgroup 1NaSodiumgroup 1RbRubidiumgroup 1CsCaesiumgroup 1FrFranciumgroup 1
# Potassium FAQ
What is the atomic number of potassium?
The atomic number of potassium is 19: every potassium atom has 19 protons in its nucleus. Its symbol is K.
What is the atomic mass of potassium?
The standard atomic mass of potassium is 39.098 u.
What is the electron configuration of potassium?
Potassium's electron configuration is [Ar] 4s¹ (1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹), with 2, 8, 8, 1 electrons per shell.
Is potassium a metal?
Yes. Potassium is an alkali metal, one of the metals.
What is the melting point of potassium?
Potassium melts at 336.53 K (63.4 °C, 146.1 °F) and boils at 1032 K (758.9 °C, 1397.9 °F).
What is potassium used for / known for?
A vital electrolyte for nerves and muscles; potash fertilisers are rich in it and bananas are a well-known dietary source.