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Potassium

Element 19 · Alkali metal

Specimen

Atomic number
19
Atomic mass
39.098
State at room temperature
Solid
Melting point
63.38 °C
Boiling point
758.9 °C
Density
0.89 g/cm³
Discovered
1807

Atomic mass from IUPAC.1 Other physical data from PubChem.2

Can I eat it?

In food and water
Your body needs it. Potassium is an essential mineral. Its benefits come mainly from fruit and vegetables. In their reference intakes, US and Canadian experts state that supplements need medical supervision, because potassium can be toxic. 34

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The atom

K
ShellElectrons
1 (K) 2
2 (L) 8
3 (M) 8
4 (N) outermost 1
Total19

Configuration [Ar] 4s¹

4s ↑
A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 19 protons. The outermost shell is shown in red. Electrons do not travel on rings: they fill orbitals, regions where an electron is likely to be found. The boxes are those orbitals for the electrons outside the Ar core, with one arrow per electron.

Related elements

Group 1
H Hydrogen Li Lithium Na Sodium Rb Rubidium Cs Caesium Fr Francium

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Sources

  1. 1

    IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW), 2024. Abridged Standard Atomic Weights 2024 .

    The atomic mass shown for the 84 elements that have a standard atomic weight.

  2. 2

    National Center for Biotechnology Information (PubChem), 2026. Periodic Table of Elements .

    Electron configuration, melting and boiling points, density and discovery year for all 118 elements.

  3. 3

    European Food Safety Authority (EFSA), 2017. Dietary Reference Values for nutrients. Summary report (amended 2019) .

    Summaries of the EFSA NDA Panel opinions on each vitamin and mineral, section 4 (minerals) and section 5 (cobalamin).

    • Potassium is an essential mineral in the human diet.
  4. 4

    Health Canada, from the Institute of Medicine (US) Dietary Reference Intakes reports, 2010. Dietary Reference Intakes tables (Institute of Medicine values), updated November 2010 , Reference Values for Elements, footnotes 20 to 27.

    The joint US and Canadian reference intakes. The values are from the Institute of Medicine reports of 1997 to 2004 and 2010.

    • The beneficial effects of potassium appear to be mainly from the forms of potassium found naturally in foods such as fruits and vegetables. Supplemental potassium should only be provided under medical supervision because of the well-documented potential for toxicity.
  5. 5

    National Institute of Standards and Technology (NIST), 2026. Atomic Weights and Isotopic Compositions for All Elements .

    Isotopic composition of each element; the most abundant isotope sets the neutron count in the nucleus view.