Potassium (K)
Potassium is element 19, a alkali metal in period 4, group 1 of the periodic table. At room temperature it is a solid.
Electron configuration [Ar] 4s1
Electrons per shell 2, 8, 8, 1
Potassium data
| Atomic number | 19 |
|---|---|
| Symbol | K |
| Atomic mass | 39.098 u |
| Category | Alkali metal |
| Group | 1 |
| Period | 4 |
| Block | s |
| State at 25 °C | solid |
| Melting point | 337 K (63.9 °C) |
| Boiling point | 1032 K (758.9 °C) |
| Density | 0.856 g/cm³ |
| Electronegativity (Pauling) | 0.82 |
| Atomic radius | 196 pm |
| 1st ionization energy | 419 kJ/mol |
| Electron affinity | -48 kJ/mol |
| Oxidation states | +1 |
| Common ion charge | + |
| Discovered | 1807 |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
Work through potassium’s configuration and its ions →
Where potassium sits
Potassium belongs to the alkali metals. Its Pauling electronegativity of 0.82 is among the lowest on the table, so it gives up electrons readily; see the electronegativity chart and periodic trends for context. To use its mass in a calculation, try the molar mass calculator.
Potassium FAQ
What is the electron configuration of potassium?
Potassium (Z = 19) has the configuration 1s2 2s2 2p6 3s2 3p6 4s1. In noble-gas shorthand that is [Ar] 4s1.
How many valence electrons does potassium have?
1 (outer shell (n = 4)).
What is the atomic mass of potassium?
The standard atomic weight of potassium is 39.098 u, so one mole weighs 39.098 g.
Is potassium a metal?
Yes. Potassium is a alkali metal.
What is the charge of a potassium ion?
Potassium most commonly forms K+.