Potassium (K) has one valence electron.
The number of valence electrons an element has is determined by its group number on the periodic table. Potassium is in Group 1 (also known as the alkali metals). Elements in Group 1 all have one valence electron. Valence electrons are the electrons in the outermost shell of an atom and are responsible for the chemical properties of the element, specifically how it bonds with other atoms. Since potassium has only one valence electron, it readily loses this electron to form a +1 ion.
