Potassium (K)
[Ar] 4s¹. 1 unpaired electron, period 4, group 1, s block.
Element or ion
Type a symbol, a name or an atomic number, add a charge such as Fe3+ or Cl-, or tap an element in the table. Orbitals fill from m = −l up, spin +½ first.
KPotassium, Z = 19, 39.098 u
[Ar] 4s1
In full: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹
- Blocks block
- Period4
- Group1
- Valence1
- Unpaired1
- MagneticPara
Last electron 4s
- n4shell
- l0s subshell
- m0orbital
- s+½spin up
Step by step
- Potassium has 19 electrons.
- Fill in (n + l) order: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹.
- Write the subshells in order of n: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹.
- Replace the argon core with [Ar]: [Ar] 4s¹.
Potassium (K): the numbers
| Atomic number | 19 |
|---|---|
| Atomic mass | 39.098 u |
| Period | 4 |
| Group | 1 |
| Block | s block |
| Valence electrons | 1 |
| Unpaired electrons | 1 |
| Magnetic | paramagnetic |
| Last electron | 4s: n = 4, l = 0, m = 0, s = +1/2 |
Potassium (K): quick answers
What is the electronic configuration of potassium?
Potassium has 19 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹, or [Ar] 4s¹ in short.
How many unpaired electrons does potassium have?
Potassium has 1 unpaired electron, so it is paramagnetic. Put one electron in each box of a subshell before pairing (Hund’s rule) to see them.
What are the quantum numbers of the last electron of potassium?
The last electron goes into 4s: n = 4, l = 0, m = 0, s = +1/2. Orbitals fill from m = −l up, spin +½ first.