The flame test of potassium.
Structure of solid potassium superoxide.
Potassium in feldspar
Sir Humphry Davy
Pieces of potassium metal
Sylvite from New Mexico
Monte Kali, a potash mining and beneficiation waste heap in Hesse, Germany, consisting mostly of sodium chloride.
Potassium sulfate/magnesium sulfate fertilizer

Chemical element with the symbol K and atomic number19.

- Potassium

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Adularia (KAlSi3O8) with pyrite (FeS2) incrustations

Orthoclase, or orthoclase feldspar (endmember formula KAlSi3O8), is an important tectosilicate mineral which forms igneous rock.

Atomic number

Charge number of an atomic nucleus.

An explanation of the superscripts and subscripts seen in atomic number notation. Atomic number is the number of protons, and therefore also the total positive charge, in the atomic nucleus.
The Rutherford–Bohr model of the hydrogen atom or a hydrogen-like ion (Z > 1). In this model it is an essential feature that the photon energy (or frequency) of the electromagnetic radiation emitted (shown) when an electron jumps from one orbital to another be proportional to the mathematical square of atomic charge (Z2). Experimental measurement by Henry Moseley of this radiation for many elements (from ) showed the results as predicted by Bohr. Both the concept of atomic number and the Bohr model were thereby given scientific credence.
Russian chemist Dmitri Mendeleev, creator of the periodic table.
Niels Bohr, creator of the Bohr model.
Henry Moseley in his lab.

Besides the case of iodine and tellurium, later several other pairs of elements (such as argon and potassium, cobalt and nickel) were known to have nearly identical or reversed atomic weights, thus requiring their placement in the periodic table to be determined by their chemical properties.

Humphry Davy

British chemist and inventor from Cornwall who invented the Davy lamp and a very early form of arc lamp.

Sir Humphry Davy, Bt
by Thomas Phillips
James Watt in 1792 by Carl Frederik von Breda
Sir Humphry Davy's Researches chemical and philosophical: chiefly concerning nitrous oxide (1800), pp. 556 and 557 (right), outlining potential anaesthetic properties of nitrous oxide in relieving pain during surgery
1802 satirical cartoon by James Gillray showing a Royal Institution lecture on pneumatics, with Davy holding the bellows and Count Rumford looking on at extreme right. Dr Thomas Garnett is the lecturer, holding the victim's nose.
Sodium metal, about 10 g, under oil
A voltaic pile
Magnesium metal crystals
Sir Humphry Davy by Thomas Lawrence
A diamond crystal in its matrix
The Davy lamp
Statue of Davy in Penzance, Cornwall, holding his safety lamp
Michael Faraday, portrait by Thomas Phillips c. 1841–1842
Davy's grave at Cimetière Plainpalais in Geneva

He is also remembered for isolating, by using electricity, several elements for the first time: potassium and sodium in 1807 and calcium, strontium, barium, magnesium and boron the following year, as well as for discovering the elemental nature of chlorine and iodine.


Chemical element with the symbol Na and atomic number 11.

Emission spectrum for sodium, showing the D line.
A positive flame test for sodium has a bright yellow color.
The structure of sodium chloride, showing octahedral coordination around Na+ and Cl− centres. This framework disintegrates when dissolved in water and reassembles when the water evaporates.
Two equivalent images of the chemical structure of sodium stearate, a typical soap.
The structure of the complex of sodium (Na+, shown in yellow) and the antibiotic monensin-A.
NaK phase diagram, showing the melting point of sodium as a function of potassium concentration. NaK with 77% potassium is eutectic and has the lowest melting point of the NaK alloys at −12.6 °C.

By means of the sodium-potassium pump, living human cells pump three sodium ions out of the cell in exchange for two potassium ions pumped in; comparing ion concentrations across the cell membrane, inside to outside, potassium measures about 40:1, and sodium, about 1:10.

Potassium hydroxide

Potassium carbonate, formed from the hydroxide solution leaking from an alkaline battery

Potassium hydroxide is an inorganic compound with the formula KOH, and is commonly called caustic potash.


Alkali is a basic, ionic salt of an alkali metal or an alkaline earth metal.

An oil painting of a chemist (Ana Kansky, painted by Henrika Šantel in 1932)

Plant potash lent the name to the element potassium, which was first derived from caustic potash, and also gave potassium its chemical symbol K (from the German name Kalium), which ultimately derived from alkali.


Salt of a fatty acid used in a variety of cleansing and lubricating products.

A handmade soap bar
Two equivalent images of the chemical structure of sodium stearate, a typical ingredient found in bar soaps.
The chemical structure of sodium laureth sulfate, a typical ingredient found in liquid soaps.
A collection of decorative bar soaps, as often found in hotels
Structure of a micelle, a cell-like structure formed by the aggregation of soap subunits (such as sodium stearate): The exterior of the micelle is hydrophilic (attracted to water) and the interior is lipophilic (attracted to oils).
Box for Amigo del Obrero (Worker's Friend) soap from the 20th century, part of the Museo del Objeto del Objeto collection
Marseille soap in blocks of 600 g
Caricature of Lillie Langtry, from Punch, Christmas 1890: The soap box on which she sits reflects her endorsements of cosmetics and soaps.
Manufacturing process of soaps/detergents
Advertising for Dobbins' medicated toilet soap
A 1922 magazine advertisement for Palmolive Soap
Liquid soap
Dudu-Osun a popular type of African black soap
Azul e branco soap – a bar of blue-white soap
Handmade soaps sold at a shop in Hyères, France
Traditional Marseille soap
Modern soap shop in Tübingen (2019)
The lye is dissolved in water.
Greases for automotive applications contain soaps

When M is Na (Sodium) or K (Potassium), the soaps are called toilet soaps, used for handwashing.


Technique that uses direct electric current to drive an otherwise non-spontaneous chemical reaction.

Illustration of a Hofmann electrolysis apparatus used in a school laboratory
Hall-Heroult process for producing aluminium

1808 – Potassium (1807), sodium (1807), barium, calcium and magnesium were discovered by Humphry Davy using electrolysis.


Polycrystalline potash, with a U.S. penny for reference. (The coin is 19 mm in diameter and copper in color.)
The first U.S. patent was issued for an improvement "in the making of Pot ash and Pearl ash by a new Apparatus and Process"; it was signed by then President George Washington.
A covered hopper car in a Canadian train for shipping potash by rail.
A postcard of the Kalium Chemicals plant in Belle Plaine, Saskatchewan
Potash evaporation ponds at the Intrepid Potash mine near Moab, Utah

Potash is the name used for various mined and manufactured salts that contain potassium in water-soluble form.

Potassium carbonate

The flame test of potassium.

Potassium carbonate is the inorganic compound with the formula K2CO3.