Potassium: Occurrence, Properties, Applications, Isotopes of Potassium


Potassium is the member of alkali metals in group 1 of the periodic table. It is represented by the symbol K. Potassium has 19 electrons and 19 protons. Its atomic number is 19 and its atomic mass is 39.

Naming and History

The word potassium is from the English word “Potash”. The chemical name of potassium is from the Latin word “kalium”. Or it may be derived from the Arabic word ‘kali’ for alkali i.e., the substances that form ashes.

In 1807, sir Humphry Davy was the first person who isolated and identified potassium as an element. It was done by electrolysis and hence the first metal isolated by this method.

He exposed the molten caustic potash and the globules of new metal were collected at the cathode.

Occurrence of Potassium

Potassium is the eighth-most abundant element on Earth. It makes about 2.1 % weight of Earth’s crust and presents as feldspars and clays. It can be found in various minerals such as sylvite, carnallite, polyhalite, and kainite.


Properties of Potassium

Potassium in its pure elemental form is a soft, waxy, and silvery-white metal that can easily be cut with a knife. When cut it oxidizes rapidly and tarnishes within minutes.

Because of highly reactive elements, they can never be found free in nature. It reacts with oxygen to form potassium superoxide and with water to form hydroxide. The amount of heat is too much that it can explode or get fire.

It has a melting point of 63 °C which is very low for a metal and a boiling point of 770 °C. Its density is 0.89 grams per cubic centimeter that means it can float over water.

Potassium in biological Systems

Potassium is essential to life. Potassium ions are present in all cells. It is essential for keeping fluid and electrolyte balance.

Plant cells are especially abundant in potassium, which they receive from the soil. Agricultural land, from which harvests are taken every year, needs to have its potassium replenished by adding potassium-based fertilizers.


The majority of potassium (95 %) enters into fertilizers and the rest goes generally into making potassium hydroxide (KOH), by the electrolysis of potassium chloride option, and after that transforming this to potassium carbonate (K2CO3).

Potassium forms an alloy with salt (NaK) that is utilized as a heat transfer medium in some types of atomic power plants or nuclear reactors.

Important substances of potassium consist of potassium superoxide, KO2, which is used in respiratory equipment, and potassium nitrate, used in fertilizers and pyrotechnics.

Potassium chloride (KCl) is the most common potassium compound. It is used in fertilizers, as a salt replacement, and to produce other chemicals.

Potassium hydroxide (KOH) is utilized to make soaps, cleaning agents, and drain cleaners.

Isotopes of Potassium

Potassium has three isotopes. One is 39 K, 40 K and 41 K. Potassium 40 and 41 are of great interest to scientists as these are used in research to study the effects and impacts on the growth of plants and cardiovascular systems of humans.

41 K is the radioisotope so it can also be used to determine the age of dead remains of animals and plants by calculating its half-life.