Factors Favouring Formation of Ionic Compounds

Ionic bonds are possible only between elements of opposite nature, i.e., one of them having a tendency to lose electrons and the other to gain electrons. Thus ionic bond formation is restricted only to most active metals (elements of group 1 and 2 and part of 13 sometimes) and the most active non-metals (elements of group 16 and 17, and nitrogen). Some transition metals also enter into ionic bond formation. 

The following factors favour formation of ionic bonds - 

Caesium, in group I has the largest size and can lose outermost electron very easily. It forms a cation most readily. In general, cations are formed easily as we go down a group. 

A very large amount of energy is required to remove a second electron from any positively charged ion. Thus, formation of a doubly charged cation Mg, Ca requires a large amount of energy, almost 4 times compared to that required for the removal of one electron. 

alkaline earth metals (group 2) form cations (M ) with less ease compared to the alkali metals (group 1). 

---