potassium [K, kalium]
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Introduction
From the English potash. The symbol K comes from the Latin kalium meaning alkali. Isolated in 1807 by Sir Humphrey Davy.
Occurrence
- 7th most abundant metal
- occurs abundantly in nature esp combined in minerals
- never found free in nature
- found in most soils
Characteristics
- silver-white soft light low-melting univalent metallic element of the alkali metal group
- 2nd least dense metal (after lithium)
- oxidizes very rapidly in air
- must be stored under argon or mineral oil
- potassium & its salts impart a lilac color to flames
- reacts with water
K + H2O -> K+ + OH- + H2 + heat
the heat generally ignites the H2 (in the presence of O2)
Uses
- metal rarely used
- salts of K+ used in
- fertilizers
- match heads
- glass
- soaps
- detergents
- K-40 isotope is used to date rocks