JEE Chemistry 2026 Question with Solution

Given: Four statements about carbon are given, and we must identify the incorrect one.

Find: Which option contains the incorrect statement.

Check each statement one by one:

1. Option A: Carbon can show negative oxidation state $-4$ in $\text{CH}_4$ and positive oxidation states such as $+2$ in $\text{CO}$ and $+4$ in $\text{CO}_2$. So this statement is correct.

2. Option B: Among the dioxides of group $14$ elements, $\text{CO}_2$ is the most acidic oxide. So this statement is correct.

3. Option C: $^{13}\text{C}$ is a stable isotope, not a radioactive one. The radioactive isotope of carbon is $^{14}\text{C}$. Therefore, this statement is incorrect.

4. Option D: Carbon has no vacant $d$-orbitals and cannot expand its octet, so its maximum covalency is four. Hence this statement is correct.

Therefore, the incorrect statement is option C.