An electrovalent bond is formed when a metal atom transfers one or more electrons to a non-metal atom.
Some other examples are: MgCl2, CaCl2, MgO, Na2S, CaH2, AlF3, NaH, KH, K2O, KI, RbCl, NaBr, CaH2 etc.
Conditions for formation of Electrovalent Bond
* The atom which changes into cation (+ ive ion) should possess 1, 2 or 3 valency electrons. The other atom which changes into anion (–ve ion) should possess 5, 6 or 7 electrons in the valency shell.
* A high difference of electronegativity (about 2) of the two atoms is necessary for the formation of an electrovalent bond. Electrovalent bond is not possible between similar atoms.
* There must be overall decrease in energy i.e., energy must be released. For this an atom should have low value of Ionisation potential and the other atom should have high value of electron affinity.