Question

The strongest bond is between
(A) CsF
(B) NaCl
(C) Both (A) and (B)
(D) None of these

Answer 1

Hint: To determine the strength of an ionic bond the difference in electronegativity of the element plays a key role. The tendency of an atom in a molecule to attract the shared pair of electrons towards itself is known as electronegativity. Greater the electronegativity difference, stronger will be the ionic bond.

Complete step by step answer:
> Fluorine is the most electronegative element on the modern periodic table. Its electronegativity value is about 3.98. Cesium is the least electronegative element on the modern periodic table. Its electronegativity value is 0.79.
> Cesium fluoride is an ionic compound. Cesium has an electronegativity of 0.79 and fluorine has an electronegativity of 3.98. When we calculate the difference between the two atoms, the difference is 3.19.
> Sodium has an electronegativity of 0.93 while Chlorine has an electronegativity of 3.16.
We take the difference of the electronegativities of sodium and chlorine that leaves us with an electronegativity difference of 2.23.
> The nature of the bond between caesium and fluorine is electrovalent ionic. As caesium is a metal, Fluorine is non-metal.
> The difference in electronegativity in CsF is greater, therefore it has a stronger ionic bond.
On the basis of fajan's rule, the anion in CsF is very small as compared to the cation. So, covalent character will be very less and ionic bonding will be very strong. Whereas in NaCl the size is anion is not too small than the size of cation. So this ionic bond is weaker than the ionic bond in CsF.

Hence we conclude that a correct answer is an option (A).

Note:
The strength of the ionic bond is directly dependent on charges and inversely dependent on the distance between the charged particles. A cation which has 2+ charges will make a stronger ionic bond than a cation with a 1+ charge. But when there is the same charge, then the electronegative factor determines the strength of the bond.