ELEMENTLE

Element 19 · Alkali Metal

Potassium

Period 4 · Group 1

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.

Three reasons Potassium stands out

  1. 1

    Important for nerve function in living organisms.

  2. 2

    A naturally occurring radioactive isotope of this element contributes to background radiation inside your own body.

  3. 3

    Its ions are essential for regulating the rhythm of the human heartbeat.

The ion behind every heartbeat

Potassium metal cannot be left in air or water, but potassium ions are indispensable inside cells. Carefully controlled flows of those ions help nerves signal and heart muscle reset between beats. Plants also require large amounts, which is why potassium compounds are a major component of fertilizer.

Potassium at a glance
Atomic number / protons19
SymbolK
Family (Elementle)Alkali Metal
Classification (PubChem)Alkali metal
Period4
Group1
Atomic mass (u)39.0983
Standard stateSolid
Electron configuration[Ar]4s1
Reported oxidation states+1
Electronegativity (Pauling)0.82
Atomic radius (pm)275
First ionization energy (eV)4.341
Electron affinity (eV)0.501
Density (g/cm³)0.89
Melting point336.53 K (63.38 °C)
Boiling point1032 K (758.85 °C)
Discovery (PubChem)1807

Values are reference data, not a specification for every temperature, pressure, or allotrope. Unknown properties are left unavailable. Superheavy-element predictions remain uncertain.

Sources & further reading

PubChem: Potassium · Potassium on Wikipedia

The introduction and original editorial story are adapted from Wikipedia contributors via Periodic-Table-JSON. Element descriptions and their adaptations are available under CC BY-SA 3.0. Numerical attributes use the PubChem periodic-table dataset, retrieved September 22, 2026.