19
K
Potassium
39.0983
Potassium (K)
Alkali MetalGroup 1Period 4s-block-block
Potassium is a chemical element with symbol K (derived from Neo-Latin, kalium) and atomic number 19. It was first isolated from potash, the ashes of plants, from which its name is derived. In the Periodic table, potassium is one of seven elements in column (group) 1 (alkali metals):they all have a single valence electron in their outer electron shell, which they readily give up to create an atom with a positive charge - a cation, and combine with anions to form salts.
Latin name: Kalium
Atomic Number
19
Atomic Mass
39.0983 g/mol
Phase (STP)
Solid
Electron Config.
[Ar] 4s¹
General
SymbolK
Atomic Number19
Atomic Mass39.0983 g/mol
CategoryAlkali Metal
Group1
Period4
Blocks-block
Electron Configuration[Ar] 4s¹
Valence Electrons1
ColourSilvery-white
Appearancesilvery gray
CAS NumberCAS7440-09-7
Physical Properties
Phase (STP)Solid
Density0.862 g/cm³
Melting Point63.38°C · 146.08°F · 336.53 K
Boiling Point758.85°C · 1397.93°F · 1032.00 K
Atomic Properties
Atomic Radius243 pm
Covalent Radius203 pm
Van der Waals Radius275 pm
Electronegativity0.82 Pauling
Ionization Energy419 kJ/mol
Electron Affinity48.4 kJ/mol
Oxidation States+1
Ion ChargeK⁺
Thermodynamic
Molar Heat29.6 J/(mol·K)
Thermal Conductivity100 W/(m·K)
Electromagnetic
Electrical TypeConductor
Crystal Structure
Crystal StructureBody-centered cubic
Mechanical Properties
Mohs Hardness0.4
Abundance
In Universe0.0003%
In Sun0.00004%
In Earth's Crust2.1000%
In Oceans0.0380%
In Humans0.2000%
In Meteorites0.1100%
Discovery & History
Discovery Year1807
Discovered ByHumphry Davy
Isotopes of Potassium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| K-39 | 93.2581% | Stable | — |
| K-40 | 0.0117% | 1.248 × 10⁹ years | β⁻, EC, β⁺ |
| K-41 | 6.7302% | Stable | — |