How can you tell that ionic bonding will placebetween metals and non metals?

Most of the time the bond between a metal and a nonmetal is ionic. However, there are some exceptions, such as BeCl2, which is covalent. The difference in electronegativity determines what kind of bond will form. Metals and nonmetals with a difference in electronegativity of >1.6 are considered to have an ionic bond.