Question

Covalent character of $ \text{NaCl} $ is more than that of $ \text{NaBr} $ .
(A) True
(B) False

Answer 1

Hint: The covalent character of an ionic compound is governed by the Fajan’s law. According to the Fajan’s Law, if two oppositely charged ions are brought together to form a compound, then the nature of the bond between them depends on the effect of ions on another.

Complete Step by Step Answer
The power of the cation to distort the electron cloud is called the polarising power of the cation and the ability of the anion to get distorted is called polarisability. According to Fajan, the smaller the size of the cation and the higher the charge on it, the more will be its polarising power. On the other hand, the bigger the size of the cation and the smaller the charge on it, the lower will be the polarising power. In case of the anions, the bigger the size and the higher the negative charge on the anion, the higher will be its polarizability and the smaller the size and lower the charge on it, lower will be its polarizability.
According to the statement above, in sodium chloride and sodium bromide, the cations are same, but the anions are different, as the size of the bromide ion is bigger than the size of the chloride ion, so it's polarisability will be higher than the chloride ion and thus sodium bromide is more covalent than sodium chloride and the above statement is “False”.

Note
A covalent bond is formed by the sharing of electrons between the atoms while the ionic bond is formed from the cations and anions due to the attractive forces in between them. But according to Fajan’s rule, there is some covalent character in between the ionic compounds and this is due to the polarizability of the anions and the polarizing power of the cations.