The number of electrons lost or gained by an atom of an element during the formation of an electrovalent bond is termed as its electrovalence. The elements which give up electrons to form positive ions have positive valence, while the elements which accept electrons to form negative ions have negative valence.

For example, during the formation of sodium chloride (Na+Cl) sodium atom (Na) loses one electron to form sodium ion(Na+) while a chlorine atom (Cl)gains an electron to form chloride ion(Cl). So, the

Electrovalence of sodium is + 1

Electrovalence of chlorine is -1