Potassium (K) – element 19
Potassium is a chemical element with the symbol K and atomic number 19. It is a alkali metal in group 1 (alkali metals), period 4 of the periodic table (s-block), and is a solid at room temperature.
Potassium (K) has atomic number 19, atomic mass 39.098 u and electron configuration [Ar] 4s1.
Potassium facts
| Symbol | K |
|---|---|
| Atomic number | 19 |
| Atomic mass | 39.098 u (g/mol) |
| Category | alkali metal |
| Group | group 1 (alkali metals) |
| Period | 4 |
| Block | s-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s1 |
| Noble-gas notation | [Ar] 4s1 |
| Electrons per shell | 2, 8, 8, 1 |
| Valence electrons | 1 |
Bohr model and shells
Potassium has 19 electrons in 4 shells: 2, 8, 8, 1. Full configuration and noble-gas notation are in the table; work out any element or ion with the electron configuration calculator.
Physical and atomic properties
| Melting point | 336.7 K (63.6 °C) |
|---|---|
| Boiling point | 1032 K (758.9 °C) |
| Density | 0.862 g/cm³ |
| Electronegativity (Pauling) | 0.82 |
| Electron affinity | 48.383 kJ/mol |
| Ionization energies | 418.8, 3052, 4420 kJ/mol (1st, 2nd, 3rd) |
| Molar heat capacity | 29.6 J/(mol·K) |
| Discovered by | Humphry Davy |
Use the atomic mass in the molar mass calculator for any formula containing K.
Position in the periodic table
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Frequently asked questions
What is the atomic mass of potassium?
The atomic mass of potassium is 39.098 u, so one mole of potassium atoms weighs 39.098 g.
What is the electron configuration of potassium?
Potassium has 19 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹, or [Ar] 4s¹ in noble-gas notation. Electrons per shell: 2, 8, 8, 1.
How many valence electrons does potassium have?
Potassium has 1 valence electron (group 1).
Is potassium a metal?
Yes. Potassium is a alkali metal.
Where is potassium on the periodic table?
Potassium is in group 1 (alkali metals), period 4, in the s-block.
Data: Periodic-Table-JSON (CC BY-SA 3.0); standard atomic weights from IUPAC (abridged). Values in brackets are the mass number of the longest-lived isotope.