Potassium

Potassium is an elementin the Alkali metals class of the periodic table. It is so chemically active that it is never found free (in elemental form) in nature. In its elemental form, it reacts with water, forming potassium hydroxide and hydrogen gas, so violently that the hydrogen usually catches fire.

Potassium
Properties
Atomic symbol	K
Atomic number	19
Classification	Alkali metal
Atomic mass	39.10 amu
Other Information
Date of discovery	1807
Name of discoverer	Davy, Sir Humphrey
Name origin	From the Latin Kalium
Uses	important biological role, and used in numerous industrial processes
Obtained from	sylvite, sylvinite, carnallite

Its existence as "potash" or "vegetable alkali" (potassium carbonate), "caustic potash" (potassium hydroxide), etc., had long been known, but it was not isolated as an element until 1807, by Sir Humphrey Davy.

The radioactive decay of potassium provides a method of radiometric dating called potassium-argon dating that is used to calculate the ages of volcanic rocks.