10 Potassium Facts

Potassium is a light metallic element that forms many important compounds and is essential for human nutrition. Here are 10 fun and interesting potassium facts.

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Potassium Facts

By Anne Marie Helmenstine, Ph.D.

1. Potassium is element number 19. This means the atomic number of potassium is 19 and each potassium atom has 19 protons.
2. Potassium is one of the alkali metals, which means it is a highly reactive metal with a valence of 1.
3. Because of its high reactivity, potassium is not found free in nature. It is formed by supernovas via the R-process and occurs on Earth dissolved in seawater and in ionic salts.
4. Pure potassium is a lightweight silvery metal that is soft enough to cut with a knife. Although the metal appears silver when it's fresh, it tarnishes so quickly that it normally appears dull gray.
5. Pure potassium usually is stored under oil or kerosene because it oxidizes so readily in air and reacts in water to evolve hydrogen, which may be ignited from the heat of the reaction.
6. The potassium ion is important for all living cells. Animals use sodium ions and potassium ions to generate electric potentials. This is vital for many cellular processes and is the basis for the conduction of nerve impulses and stabilization of blood pressure. When not enough potassium is available in the body, a potentially fatal condition called hypokalemia can occur. Symptoms of hypokalemia include muscle cramps and irregular heartbeat. An overabundance of potassium causes hypercalcemia, which produces similar symptoms. Plants require potassium for many processes, so this element is a nutrient that is readily depleted by crops and must be replenished by fertilizers.
7. Potassium was first purified in 1807 by Cornish chemist Humphry Davy (1778–1829) from caustic potash (KOH) via electrolysis. Potassium was the first metal to be isolated using electrolysis.
8. Potassium compounds emit a lilac or violet flame color when burned. It burns in water, just like sodium. The difference is that sodium burns with a yellow flame and is more likely to shatter and explode! When potassium burns in water, the reaction releases hydrogen gas. The heat of the reaction can ignite the hydrogen.
9. Potassium is used as a heat transfer medium. Its salts are used as a fertilizer, oxidizer, colorant, to form strong bases, as a salt substitute, and for many other applications. Potassium cobalt nitrite is a yellow pigment known as Cobalt Yellow or Aureolin.
10. The name for potassium comes from the English word for potash. The symbol for potassium is K, which is derived from the Latin kalium and Arabic qali for alkali. Potash and alkali are two of the potassium compounds known to man since ancient times.

More Potassium Facts

• Potassium is the seventh most abundant element in the Earth's crust, accounting for about 2.5% of its mass.
• Element number 19 is the eighth most abundant element in the human body, accounting for between 0.20% and 0.35% of body mass.
• Potassium is the second lightest (least dense) metal after lithium.
• Three isotopes of potassium occur naturally on Earth, although at least 29 isotopes have been identified. The most abundant isotope is K-39, which accounts for 93.3% of the element.
• The atomic weight of potassium is 39.0983.
• Potassium metal has a density of 0.89 grams per cubic centimeter.
• The melting point of potassium is 63.4 degrees C or 336.5 degrees K and its boiling point is 765.6 degrees C or 1038.7 degrees K. This means potassium is a solid at room temperature.
• Humans can taste potassium in aqueous solution. Dilute potassium solutions to taste. Increasing the concentration leads to a bitter or alkaline flavor. Concentrated solutions taste salty.
• One lesser-known use of potassium is as a portable oxygen source. Potassium superoxide (KO₂), is an orange solid used to release oxygen and absorb carbon dioxide in the respiration system for submarines, spacecraft, and mines.

Sources

• Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press.
• Marx, Robert F. (1990). The history of underwater exploration. Courier Dover Publications. p. 93.
• Shallenberger, R. S. (1993). Taste chemistry. Springer.