Final answer:
The rule for bonding and antibonding molecular orbitals in heteronuclear diatomic molecules' MO diagrams is that they form one of each per pair of atomic orbitals, and the bonding MOs are skewed towards the more electronegative atom, causing a polar bond.
Step-by-step explanation:
The question is asking about the characteristics of bonding and antibonding molecular orbitals in heteronuclear diatomic molecules when constructing molecular orbital (MO) energy-level diagrams. In MO theory, the number of molecular orbitals is the same as the number of atomic orbitals that interact. When two nonidentical atoms form a molecule, there will be one bonding (lower-energy) and one antibonding (higher-energy) molecular orbital for each pair of interacting atomic orbitals.
The atomic orbitals of the more electronegative atom will be at a lower energy level, causing a skewed MO diagram with the bonding molecular orbitals being closer to the energy levels of the more electronegative atom's atomic orbitals. This leads to a polar covalent bond as the electron density is more concentrated around the more electronegative atom.