Fajans' rules

Fajans' rules help predict whether an ion will favor forming an ionic or covalent bond. They indicate that a small, highly charged metal cation (a positive ion) tends to attract electrons strongly, making the bond more covalent. Conversely, a large, highly charged nonmetal anion (a negative ion) can also share electrons more covalently. Factors like the ion's size and charge influence electron sharing: smaller, highly charged ions increase covalent character, while larger, less charged ions favor ionic bonds. Overall, Fajans’ rules analyze how the charge and size of ions influence the likelihood of electron sharing versus transfer in bonding.