9. Explain why you can't write the formula of the ionic compound that forms between Fe
and S?

See explanation

Explanation:

According to Fajan's rules, the degree of covalent character of a bond depends on the relative polarizing power of ions.

Generally, ions become more polarizing when they are small and highly charged. Large negative ions are more polarizable than small ones.

A very small positive charge concentrated on a small area such as in Fe^2+ makes the ion highly polarizing. Also, a large negative ion such as S^2- is highly polarizable.

As a result of these FeS has considerable covalent character hence we can not simply write the formula of the ionic compound that forms between Fe and S?