Choose the INCORRECT statement

We need to identify the INCORRECT statement about carbon and Group 14 elements.

Option A: "Carbon cannot exceed its covalency more than four." - TRUE. Carbon has no d-orbitals in its valence shell, so max covalency is 4.

Option B: "Carbon exhibits negative oxidation states along with +4 and +2." - TRUE. Carbon can show -4 (CH₄), +2, +4 oxidation states.

Option C: "Among the isotopes of carbon, ¹³C is a radioactive isotope." - INCORRECT. ¹³C is a stable isotope. It is ¹⁴C that is radioactive.

Option D: "CO₂ is the most acidic oxide among the dioxides of group 14 elements." - TRUE. CO₂ is the most acidic oxide; acidity decreases down the group (SiO₂, GeO₂ are less acidic; SnO₂, PbO₂ are amphoteric).

Therefore, the incorrect statement is Option 3: ¹³C is a radioactive isotope.