POTASSIUM

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Overview

Potassium is an alkali metal on the periodic table represented by the symbol K. Its atomic number is 19 and its standard atomic weight is 39.0983. Potassium is a silvery grey metal at room temperature and it reacts quickly with water and air. It has 24 known isotopes (3 are found naturally on earth). Potassium-39 has 19 protons, 19 electrons, and 20 neutrons.


Sir Humphry Davy first isolated metallic potassium in 1807. He extracted it from caustic potash by using electrolysis.[1]

potassium atom

Alkali Metals Group

Potassium is the third element down in the 1st group of the periodic table, the alkali metals, along with Lithium, Sodium, Rubidium, Caesium, and Francium. The alkali metals have more in common than any other group.[2]


Common properties and trends:

  • 1 valence electron
  • Never found as a free element
  • Least dense metals on the periodic table
  • High electrical conductivity[3]
  • Increasing reactivity down group[4]
  • Decreasing electronegativity down group

Reactions

Reaction With water

Like other alkali metals, Potassium reacts violently in water.[5] The chemical equation is

2K + 2H2O → 2KOH + H2. 2 Potassium (K) atoms react with 2 water (H2O) molecules to form 2 Potassium Hydroxide (KOH) molecules and 1 molecule of Hydrogen (H) gas, releasing energy in the process. This is an example of a single replacement reaction.

Potassium in Water (reaction only)

Potassium Chloride

Potassium Chloride (KCl) is compound made from one atom of Potassium and one atom of Chloride. It forms an ionic bond and it is a diatomic compound with a linear shape.

Composition:

  • 52.45% Potassium
  • 47.55% Chlorine

Specific Heat

The specific heat of Potassium is 0.757 J/(g K). To raise the temperature of 100 grams of Potassium 25 degrees celsius, it would take 1892.5 J. The melting point is 63.38 degrees celsius and the boiling point is 759 degrees celsius.

Uses

One of the main uses for Potassium is fertilizer, as it is necessary for plants to be healthy. It is found in most soil types but needs to be replenished in between harvests.


A compound containing Potassium, Potassium Chloride, is used for a variety of purposes from replenishing electrolytes[6] to causing cardiac arrest in lethal injections.

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Sources

[1] Enghag, Per. Encyclopedia of the Elements: Technical Data, History,

Processing, Applications. Weinheim: Wiley-VCH, 2004. Wikipedia. Web.


[2] "Periodic Table: Trends." Www.rsc.org. Royal Society of Chemistry, 2015.

Web. 14 Dec. 2015.


[3] Greenwood, N. N., and A. Earnshaw. Chemistry of the Elements, Second

Edition. N.p.: Butterworth-Heinemann, 1997. Wikipedia. Web. 14 Dec. 2015.


[4] "Reactions of Alkali Metals." BBC News. BBC, 2014. Web. 14 Dec. 2015.


[5] Clark, Jim. "Reactions of the Group 1 Elements with Water." Reactions of the

Group 1 Elements with Water. N.p., Feb. 2015. Web. 14 Dec. 2015.


[6] Garth, David. "Hypokalemia in Emergency Medicine Treatment & Management." Hypokalemia in Emergency Medicine Treatment & Management: Prehospital Care, Emergency Department Care, Consultations. Medscape, 30 Oct. 2015. Web. 14 Dec. 2015.