Potassium (K)

Silvery-white metal

Potassium is a soft, silvery metal that reacts explosively with water and is vital for nerve function, and its single 4s¹ electron has a very low ionization energy (418.8 kJ/mol), making it even more reactive than sodium. It is essential for maintaining cell membrane potential and muscle contraction.

Key metrics

Density0.862g/cm³

Melting point336.5K

Boiling point1,032K

Electronegativity0.82Pauling

Discovery

1807discovered

Discovered by: Humphry Davy
Reactivity profile: Extremely Reactive with Water
Reactivity: High
Bonding: Metallic

Electron configuration

\textcolor{#6b7280}{[Ar]}\; \textcolor{#ef4444}{4_{s}^{1}}

[Ar] 4s1

Wave function

\Psi_{\text{K}} \approx \frac{1}{\sqrt{19!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{19}(\mathbf{r}_{19}) \right|

Probability density $|\Psi|^2$ across the K valence shell.

Crystal structure

Body-Centered Cubic

Lattice constantsa = 1.00

Cell anglesα = β = γ = 90°

Coordination number8

Atoms per cell2

Atomic packing factor0.68

Physical properties

Atomic radius: 227 pm
Ionization energy: 419 kJ/mol
Electron affinity: 48.4 kJ/mol
Crystal structure: Body-centered cubic (bcc)

Oxidation states

Acid/base

Basic

Strongly acidicStrongly basic

State at 25 °CSolid

336.5 K1032 K298 K

Emission spectrum

3 transitions

380450500550600650700780

VioletBlueGreenYellowRed

404.4nmK I (violet)Violet30%

766.5nmK I (red)IR100%

769.9nmK I (red)IR100%

Dominant line 769.9 nmRange 404–770 nmTransitions 3