Potassium

Definition - What does Potassium mean?

Potassium is a chemical element in the family of alkali metals with the chemical symbol K and atomic number 19 because it has 19 protons in its nucleus. Potassium metal has a silvery luster, is soft and is easily cut. As with other alkali metals, potassium in its neutral form, potassium metal, is not found in nature because that form reacts violently with water to produce potassium hydroxide and hydrogen gas:

2 K (s) + 2 H2O (l) = 2 KOH (aq) + H2 (g)

The reaction is explosive and highly dangerous. Potassium metal is a very strong reducing agent and readily transfers a single electron to reduce another molecule and create a potassium salt with potassium in the +1 oxidation state (K+). Common potassium salts include potassium chloride (KCl) and potassium hydroxide (KOH), which are soluble in water. KOH, being a strong base, is used in acid neutralization and saponification.

The K+ ion plays important roles in biological systems, making it an important component of fertilizers and food such as bananas.

Corrosionpedia explains Potassium

Naturally occurring potassium is composed of 93.26% of the isotope 39K, which has 20 neutrons, and 6.73% 41K with 22 neutrons and 0.01% 40K with 21 neutrons. Due to its extreme reactivity with air, potassium metal must be handed under special environments filled with inert gases. Once oxidized to produce K+, potassium becomes highly inert and difficult to reduce back to its metallic form.

Properties of potassium metal:

  • Molecular mass: 39.09 g/mol
  • Density (at 20°C): 0.862 g/cm3
  • Melting point: 63.5°C (146°F)
  • Boiling point: 759°C (1,398°F)

Potassium has critical functions in biology, including the modulation of cellular membrane potentials critical for neuron function and muscular tissue function. Also important in plant nutrition, potassium salts are used in fertilizers.

Potassium metal is used only rarely in chemical research when a powerful reductant is needed for a special application. Otherwise, usage revolves around basic potassium salts such as potassium chloride, potassium carbonate, and potassium hydroxide. Potassium hydroxide is used for neutralizing or modulating pH, the production of soaps and the hydrolysis of esters.

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