JEE Chemistry 2023 Question with Solution

Given: We need the correct order of bond enthalpy for C -- C, Si -- Si, Ge -- Ge, and Sn -- Sn bonds.

Find: Which option matches the decreasing bond enthalpy order.

Bond enthalpy generally decreases down a group because atomic size increases and bond length becomes larger, making the bond weaker.

For Group $14$ elements, the atomic size order is:

$$\text{C} < \text{Si} < \text{Ge} < \text{Sn}$$

Therefore, bond enthalpy decreases in the reverse order:

$$\text{C-C} > \text{Si-Si} > \text{Ge-Ge} > \text{Sn-Sn}$$

This corresponds to option D. However, the solution states The Correct Option is A, which disagrees with its own working. Using the solution working, the correct option is D.