Question

The bond dissociation energies for single covalent bonds formed between carbon and A, B, D and E atoms are:

Bond	Bond energy $kcal{mol}^{-1}$
(i) $C-A$	240
(ii) $C-B$	382
(iii) $C-D$	276
(iv) $C-E$	486

This indicates that the smallest atom is:
A. A
B. B
C. D
D. E

Answer 1

Hint: The strength of a covalent bond depends upon the amount of energy that would be required to break the bond. This energy is known as bond energy.

Complete step by step answer:
The bond energy also known as the bond enthalpy or the bond strength is the amount of energy that is required to break a bond or a mole of a molecule into its constituent atoms.
So, the higher will be the bond energy, the stronger will be the bond. And the bond energy increases with the decrease in the size of an atom.
This is due to the fact that a small atom will have a large nuclear force of attraction with the electrons on the outermost shell of the nucleus, hence more bond energy would be required to break the bond.
Now, keeping the above relations in mind, the decreasing order of bonds in terms of the bond energies is: $C-E > C-B > C-D > C-A$. Hence, the increasing order of the atoms according to the size is: $E < B < D < A$. Therefore, the smallest atom is E.

Hence, option (d) is the correct answer.

Note: Covalent bonds are stronger types of bonds. This is due to the fact that they have a shared pair of electrons which makes them stable by keeping the atoms together. Their strength also depends upon the overlap that exists between the valence orbitals of the bonded atoms.