Potassium is not inert in nature. It is a reactive alkali metal. The potassium atom has 19 electrons in its electron shell with a configuration of 2, 8, 10, 1. This is one more than the nearest noble gas configuration of 2, 8, 10. The potassium atom has to lose one electron to achieve a stable electron configuration.
Potassium atoms take part in reactions with elements that can accept an electron. The result is an ionic compound with a positively charged potassium ion and another negatively charged ion. The two oppositely charged ions are attracted to each other as the net charge becomes zero.