potassium

Potassium

potassium (K)

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atomic number & mass number

19 39.0983

Electron Configuration

[Ar] 4s1

The English name for the element potassium comes from the word potash and refers to the method by which potash was obtained leaching the ash of burnt wood or tree leaves and evaporating the solution in a pot. Potash is primarily a mixture of potassium salts because plants have little or no sodium content, and the rest of a plant's major mineral content consists of calcium salts of relatively low solubility in water. potassium was first founded in 1702 but was first isolated in 1807

The only common oxidation state for potassium is +1. Potassium metal is a powerful reducing agent that is easily oxidized to the monopositive cation, K+. Once oxidized, it is very stable and difficult to reduce back to the metal. Potassium is an extremely active metal, which reacts violently with oxygen and water in air. With oxygen, it converts to potassium peroxide and with water potassium hydroxide. The reaction of potassium with water is dangerous because of its violent exothermic character and the production of hydrogen gas. Hydrogen reacts again with atmospheric oxygen, producing water, which reacts with the remaining potassium. This reaction requires only traces of water; because of this, potassium and its liquid alloy with sodium NaK are potent desiccants that can be used to dry solvents prior to distillation. Potassium does not react with most hydrocarbons, such as mineral oil or kerosene. It readily dissolves in liquid ammonia, up to 480 g per 1000 g of ammonia at 0 °C. Depending on the concentration, the ammonia solutions are blue to yellow, and their electrical conductivity is similar to that of liquid metals. In a pure solution, potassium slowly reacts with ammonia to form KNH2, but this reaction is accelerated by minute amounts of transition metal salts.It can reduce the salts to the metal; potassium is often used as the reductant in the preparation of finely divided metals from their salts by the Rieke method.

Humphry davy derived potassium from caustic potash by the use of electrolysis of the molten salt with the newly discovered voltaic pile