Potassium (K): Electron Configuration, Properties and Uses
Potassium (K): Electron Configuration, Properties and Uses
Electron configuration [Ar] 4s1 · group 1 · period 4 · Ar 39.098
Potassium data
- Atomic number
- 19
- Relative atomic mass
- 39.098
- Group
- 1
- Period
- 4
- Block
- s
- Category
- Alkali metal
- Electron configuration
- [Ar] 4s1
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s1
- Electrons per shell
- 2, 8, 8, 1 (K L M N)
- Valence electrons
- 1
- Electronegativity (Pauling)
- 0.82
- First ionisation energy
- 4.341 eV
- Atomic radius (van der Waals)
- 275 pm
- State at room temperature
- Solid
- Melting point
- 63.4 °C
- Boiling point
- 759 °C
- Density
- 0.89 g/cm³
- Common oxidation states
- +1
- Discovered
- 1807
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 8 · N 1
Orbital diagram (outer electrons)
About potassium
With atomic number 19, potassium (K) has 19 protons in its nucleus and 19 electrons as a neutral atom. It is an alkali metal in group 1, period 4, s-block. The element was discovered in 1807. The symbol K comes from the Latin kalium. Potassium is a solid at room temperature, melting at 63.4 °C and boiling at 759 °C. Its density of 0.89 g/cm³ is lower than water, so the metal floats.
Potassium electron configuration
The electron configuration of potassium is 1s2 2s2 2p6 3s2 3p6 4s1, or in short [Ar] 4s1. Its electrons occupy 4 shells: K = 2, L = 8, M = 8, N = 1. Potassium has 1 valence electron in the N shell (4s1), which is why it sits in group 1. When it forms cations, electrons leave the outermost subshell first: K+ = [Ar] (like argon).
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18) → 4s1(19)
Uses of potassium
In industry and the laboratory, potassium turns up in many places, for example KCl and potassium nitrate fertilisers, soft soap (KOH), an essential body electrolyte, and potassium permanganate as an oxidant. For research and analysis you can browse potassium compounds in the AMI Scientific catalogue.
Safety
Potassium metal reacts with water even more violently than sodium and can ignite, so it is stored under mineral oil. Always read the safety data sheet (SDS) before working with a chemical.
Other elements in group 1
Frequently asked questions
What is the electron configuration of potassium?
The electron configuration of potassium (K, atomic number 19) is 1s2 2s2 2p6 3s2 3p6 4s1, or [Ar] 4s1 in short. By shell: 2, 8, 8, 1.
How many valence electrons does potassium have?
Potassium has 1 valence electron.
Which group and period is potassium in?
Potassium is in group 1, period 4, s-block.
What is the atomic mass of potassium?
The relative atomic mass of potassium is 39.098. Use it to calculate molar mass with the molar mass calculator.
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