K
Potassium
Element 19 · Alkali metal
Potassium (K)
Potassium is a soft alkali metal that reacts violently with water, burning with a lilac flame. It is vital for nerve and muscle function.
- Alkali metal
- Period 4
- Group 1
- s-block
- solid at room temperature
Key properties
- Atomic mass
- 39.0983
- u
- Electron configuration
- [Ar] 4s1
- Melting point
- 63.4 °C
- 336.53 K
- Boiling point
- 758.9 °C
- 1,032 K
- Density
- 0.89 g/cm³
- Electronegativity
- 0.82
- Pauling
- Atomic radius
- 275 pm
- van der Waals
- 1st ionisation energy
- 4.341 eV
Compare with every element:Electronegativity chartAtomic radius chartIonisation energy chartDensity chart of the elementsMelting point chartElectron configuration chart
Did you know?
Notable facts about potassium
- 01
Potassium was the first metal isolated by electrolysis, a few days before sodium.
- 02
Bananas are famous for potassium, but potatoes and beans contain more per serving.
- 03
Naturally radioactive potassium-40 makes the human body give off about 4,000 decays per second.
Applications
What is potassium used for?
- Fertilisers (potash)
- Soap making
- Food salt substitutes
- Glass manufacture
History
Discovery & name origin
Discovered by
Year
Where
England
Name origin
English potash; the symbol K comes from Latin kalium.
Atomic structure
Atomic properties
Atomic structure
Atomic properties
- Atomic number
- 19
- Atomic mass
- 39.0983 u
- Group
- 1
- Period
- 4
- Block
- s-block
- Electron configuration
- [Ar] 4s1
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s1
- Electrons per shell
- 2, 8, 8, 1
- Electronegativity (Pauling)
- 0.82
- Electron affinity
- 0.501 eV
- Atomic radius (van der Waals)
- 275 pm
- Stable isotopes
- 2
Oxidation states
Highlighted: common oxidation states (+1).
Successive ionisation energies
Energy to remove each electron in turn (kJ/mol). Big jumps show where a new, inner shell begins.
- 1st418.8
- 2nd3,052
- 3rd4,420
- 4th5,877
- 5th7,975
- 6th9,590
- 7th11,343
- 8th14,944
Physical
Physical properties & colour
Physical
Physical properties & colour
- State at 20 °C
- Solid
- Melting point
- 336.53 K · 63.4 °C · 146.1 °F
- Boiling point
- 1,032 K · 758.9 °C · 1,397.9 °F
- Density
- 0.89 g/cm³
- Molar heat capacity
- 29.6 J/(mol·K)
- Appearance
- Silvery grey
- CPK model colour
- Copied
The CPK colour is the convention used for this element’s atoms in molecular models.
FAQ
Potassium questions
What is K on the periodic table?
K is the symbol for potassium, element 19 on the periodic table. It sits in group 1, period 4, in the alkali metal category, and has an atomic mass of 39.0983.
What is the atomic number of potassium?
Potassium has atomic number 19, so every potassium atom has 19 protons in its nucleus. Its symbol is K and its atomic mass is 39.0983.
Who discovered potassium?
Potassium was discovered by Humphry Davy in 1807 (England). The name comes from English potash; the symbol K comes from Latin kalium.
What is potassium used for?
Potassium is used for: fertilisers (potash); soap making; food salt substitutes; glass manufacture.
Is potassium a metal?
Yes. Potassium is a alkali metal, one of the metallic elements.
What is the electron configuration of potassium?
The electron configuration of potassium is [Ar] 4s1. Its 19 electrons are arranged in shells as 2, 8, 8, 1.