Which set of conditions supports strong mixing between two atomic orbitals?

• Suitable symmetry, nonzero overlap and a small energy gap
• Suitable symmetry, zero overlap and a small energy gap
• Suitable symmetry, nonzero overlap and a very large energy gap

In an interacting two-orbital model with unequal parent energies, which parent contributes more to the bonding combination?

• The higher-energy parent orbital
• The two parent orbitals equally
• The lower-energy parent orbital

In an interacting two-orbital model with unequal parent energies, the antibonding combination has more character from the higher-energy parent.

In a two-orbital model, hold the nonzero interaction fixed while increasing the parent energy gap. What happens to the orbital contributions?

• More mixing and less localisation on the parent orbitals
• More mixing and more localisation on the parent orbitals
• Less mixing and more localisation on the parent orbitals

HF's F 2p_z orbital lies below H 1s and contributes more to their bonding combination. Which partial charges follow, and what must a full molecular-dipole calculation include?

• H partially negative, F partially positive; include all electrons and nuclei to obtain the full dipole.
• H partially positive, F partially negative; include all electrons and nuclei to obtain the full dipole.
• H partially positive, F partially negative; use the bonding orbital alone to obtain the full dipole.

Fill CO's 10 valence electrons from low to high: 3sigma, 4sigma, 1pi pair, 5sigma, 2pi* pair, 6sigma*. Which option gives the electron count in each set and the usual terminal donor? Each pi entry counts both orbitals.

• 2,2,4,2,0,0; 5sigma pair donates through carbon.
• 2,2,4,2,0,0; 5sigma pair donates through oxygen.
• 2,2,2,2,2,0; 5sigma pair donates through carbon.

Linear CO2 has two equivalent polar C=O bonds but no permanent molecular dipole. Why?

• Equal polar bonds give opposite contributions, which cancel in linear CO2.
• Equal polar bonds give parallel contributions, which cancel in linear CO2.
• Equal polar bonds give opposite contributions, which double in linear CO2.

Take the HF bond as the z axis. A student says H 1s and F 2p_x must mix strongly if their energies are equal. What is missing?

• Equal energies alone guarantee strong mixing, even with different sigma and pi symmetries about z.
• H 1s is sigma and F 2p_x is pi, so their net overlap is zero.
• The two orbitals must have equal sizes.