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Potassium

K

Atomic Number: 19
Atomic Weight: 39.0983
Element Type: Alkali Metal
Crystal Structure: Cubic Face Centered
Melting Point: 63.38°C = 146.084°F = 336.53 K
Boiling Point: 759.0°C = 1398.2°F = 1032.15 K
Critical Temp: °C = °F = K
Atomic Radius: 2.77 Å (Å = Angstrom = 10-10 m)
Covalent Radius: 2.03 Å
Electronegativity: 0.82

Discovery

(English, potash - pot ashes; L.. kalium, Arab qali, alkali) Discovered in 1807 byDavy, who obtained it from caustic potash (KOH); this was the first metal isolated byelectrolysis.

Sources

Potassium is the 7th most abundant element on earth, making up 2.4% of the earth's crust, by weight. Potassium is not found free in nature. Potassium was the first metal isolated by electrolysis (Davy, 1807, from caustic potash KOH). Thermal methods (reduction of potassium compounds with C, Si, Na, CaC2) are also used to produce potassium. Sylvite, langbeinite, carnallite, and polyhalite form extensive deposits in ancient lake and sea beds, from which potassium salts can be obtained. In addition to other locations, potash is mined in Germany, Utah, California, and New Mexico.

Uses
Potassium's melting point is 63.25°C, boiling point is 760°C, specific gravity is 0.862 (20°C), with a valence of 1. Potassium is one of the most reactive and electropositive of metals. The only metal that is lighter than potassium is lithium. The silvery white metal is soft (easily cut with a knife). The metal must be stored in a mineral oil, such as kerosene, as it oxidizes rapidly in air and catches fire spontaneously when exposed to water. Its decomposition in water evolves hydrogen. Potassium and its salts will color flames violet.


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