12. Molecular Shapes & Valence Bond Theory

What are the factors that govern the degree of overlap of atomic orbitals on different atoms?

Which of the following statements about localized and delocalized 𝜋 bonding are true?

a. In a localized 𝜋 bond, the two electrons in the bond are associated totally with two atoms.

b. A molecule or ion that has multiple resonance structures with double bonds exhibits delocalized 𝜋 bonding.

c. In a delocalized 𝜋 bond, the electrons are spread among three or more atoms.

d. Benzene is best described using localized 𝜋 bonding.

Which of the following statements about molecular orbitals are true?

a. A molecular orbital can hold a maximum of two electrons.

b. The number of molecular orbitals formed equals the number of atomic orbitals that are mixed to form the MOs.

c. A bonding molecular orbital will have a lower energy than that of the two atomic orbitals that are mixed to make the MO.

d. Electrons cannot be put in antibonding molecular orbitals.

e. A bonding molecular orbital concentrates electron density in the region between two atoms.

The figures show two different possible combinations of two 2p atomic orbitals with phases to form a molecular orbital. For each of these figures

a. identify whether it represents constructive or destructive addition of the two atomic orbitals, and

b. identify whether the resulting molecular orbital will be a 𝜎, 𝜎∗, 𝜋, or 𝜋∗ MO. [Section 9.8]