Final answer:
In cumulene, there is both sigma and pi overlap of orbitals. The correct answer is option A
Step-by-step explanation:
In cumulene molecules, the primary types of orbital overlap involve sigma (σ) and pi (π) bonds. Option A) Sigma and pi overlap is the correct choice. Cumulenes consist of a chain of consecutive double bonds separated by single bonds. The sigma bonds (σ) are formed through head-on overlap of atomic orbitals between adjacent carbon atoms connected by single bonds, while the pi bonds (π) result from the side-to-side overlap of p orbitals from these carbon atoms within the double bonds. This sigma-pi alternation characterizes the unique structure of cumulene molecules.
Options B, C, and D suggest combinations involving other orbital types such as delta (δ) and gamma (γ) overlap, which are not typically associated with the bonding pattern found in cumulene molecules. Therefore, option A accurately reflects the dominant types of orbital overlap present in cumulenes.