19K39.098
Potassium
Alkali metals · solid at STP · Block S
About
Potassium is a soft, silvery-white alkali metal that reacts violently with water, producing flammable hydrogen gas. It is an essential mineral and electrolyte for human health, crucial for nerve function, muscle contraction, and maintaining fluid balance. Its compounds, particularly potassium chloride, are a major component of agricultural fertilizers, vital for plant growth.
Atomic Properties
Atomic Number19
Atomic Weight39.098 u
Neutrons (common)20
Electron Configuration[Ar] 4s¹
Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹
Electrons per Shell2, 8, 8, 1
Electronegativity0.82
Electron Affinity48.4 kJ/mol
Oxidation States+1, 0
Covalent Radius196 pm
Van der Waals Radius275 pm
Ionic Radius138 pm
Periodic Table Position
Group1
Period4
BlockS
Chemical SeriesAlkali metals
Physical Properties
State at STPsolid
Appearancesilvery-grey metal
Crystal Structurebcc
Magnetic Orderingparamagnetic
Speed of Sound2,000 m/s
Poisson Ratio0.35
Thermal Properties
Melting Point336.7 K
Boiling Point1,032 K
Triple Point336.5 K
Thermal Expansion0 1/K
Thermal Conductivity102.5 W/(m·K)
Specific Heat0.757 J/(g·K)
Molar Heat29.6 J/(mol·K)
Heat of Fusion2.33 kJ/mol
Heat of Vaporization76.9 kJ/mol
Abundance
In Earth's Crust20,900 ppm
In Ocean380 ppm
In Solar System3.6 ppm
In Human Body2,000 ppm
In Universe3 ppm
Discovery
Discovered byHumphry Davy
Discovery Year1,807
Occurrenceprimordial
CAS Number7440-09-7
Electron Configuration
Energy
↿⇂
↿⇂
↿⇂
↿⇂
↿⇂
↿⇂
↿⇂
↿⇂
↿⇂
↿
3d
4p
5s
4d
5p
6s
4f
5d
6p
7s
5f
6d
7p
Isotopes of Potassium
| Symbol ▲ | Mass (u) ▲ | Abundance ▲ | Half-life ▲ | Decay Mode ▲ |
|---|---|---|---|---|
| 39K | 38.963706 | 93.2581% | Stable | Stable |
| 40K | 39.963998 | 0.0117% | 1.248 Gy | Beta Minus Decay, Electron Capture |
| 41K | 40.961825 | 6.7302% | Stable | Stable |
| 42K | 41.962402 | — | 12.355 h | Beta Minus Decay |
Interactive Visualization
Explore the 3D Bohr model of Potassium in our interactive viewer.
View 3D Model of Potassium