Metal ions having variable oxidation number can form more than one types of binary compound. Fe shows +2,+3 oxidation states. Thus, it can form FeCl3,FeCl2. Related Theory Binary compounds are chemical compounds comprising of two distinct elements. For example, water, calcium chloride etc. Caution Zn, even being a transition metal shows only +2 oxidation state, due to fully filled 3d subshell.