Potassium (chemical symbol - K, from Lat. Kalium) is a chemical element of the 1st group (according to the outdated classification - the first group of the main subgroup, IA), the fourth period of the periodic system of chemical elements of D. I. Mendeleev, with atomic number 19.
A simple substance potassium is a soft alkaline metal of silvery-white color. In nature, potassium is found only in compounds with other elements, for example, in seawater, as well as in many minerals.
It oxidizes very quickly in air and very easily enters into chemical reactions, especially with water, forming an alkali.
In many properties, potassium is very close to sodium, but from the point of view of biological function and use by cells of living organisms, they are antagonistic.
