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Potassium ions are necessary for the function of all living cells.The transfer of potassium ions through nerve cell membranes is necessary for normal nerve transmission; potassium deficiency and excess can each result in numerous abnormalities, including an abnormal heart rhythm and various electrocardiographic (ECG) abnormalities.In the periodic table, potassium is one of the alkali metals.All of the alkali metals have a single valence electron in the outer electron shell, which is easily removed to create an ion with a positive charge – a cation, which combines with anions to form salts. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and reacts vigorously with water, generating sufficient heat to ignite hydrogen emitted in the reaction and burning with a lilac-colored flame.
This reaction requires only traces of water; because of this, potassium and the liquid sodium-potassium (Na K) alloy are potent desiccants that can be used to dry solvents prior to distillation.It is found dissolved in sea water (which is 0.04% potassium by weight), and is part of many minerals.Potassium is chemically very similar to sodium, the previous element in group 1 of the periodic table.It is a soft solid with a low melting point, and can be easily cut with a knife.Freshly cut potassium is silvery in appearance, but it begins to tarnish toward gray immediately on exposure to air.
Most industrial applications of potassium exploit the high solubility in water of potassium compounds, such as potassium soaps.