Worksheet: Molecular Orbital Theory
In this worksheet, we will practice describing the shapes, energies and electron occupancies of bonding, nonbonding, and antibonding molecular orbitals.
An sp2 hybridized atom in a molecule forms bonds to three other atoms of the same element. There are no other bonds in the molecule. Which of the following statements is true?
- AThe dipole moment of each bond is zero.
- BThe three bonds contribute equally to each bonding molecular orbital.
- CAll of the bonds are partial double bonds.
- DThe three bonds contribute equally to each bonding energy level.
- EThe molecular bonding orbitals have the same energy.
What is the main reason that bonding molecular orbitals are lower in energy than the parent atomic orbitals?
- AThe electrons in a bonding orbital repel each other more weakly.
- BThe electrons in a bonding orbital are attracted to more than one atomic nucleus.
- CThe electrons in a bonding orbital are more weakly shielded by the core electrons of the parent atoms.
- DBonding orbitals are less symmetrical than atomic orbitals.
- EThe electrons in a bonding orbital have a lower orbital angular momentum.
Which of the following statements is false?
- AWhen atomic orbitals overlap to form molecular orbitals, the total number of orbitals does not change.
- BThe greatest overlap between an atomic orbital and a antibonding orbital is produced when the atomic orbital approaches the bond axis at .
- CThe greatest overlap between an atomic orbital and a antibonding orbital is produced when the atomic orbital approaches parallel to the bond axis.
- DWhen two p orbitals overlap to form a bond, most of the electron density is concentrated between the nuclei.
- EMolecules containing an even number of electrons can be paramagnetic.
Which of the following statements is true?
- AIn the lowest-energy state of a stable molecule, electrons never occupy an antibonding orbital.
- BIf a molecule contains multiple bonds, the highest-energy occupied orbitals are always bonding orbitals.
- CMolecules containing an odd number of electrons are always paramagnetic.
- DIn the lowest-energy state of a stable molecule, electrons in bonding orbitals are always paired.
- EOnly two atoms can contribute to a bonding orbital.
The average bond energy of a single bond is 347 kJ/mol, while that of a triple bond is 839 kJ/mol. Why is a triple bond between carbon atoms not three times as strong as a single bond?
- ABonds formed by p orbitals are always weaker than those formed by hybrid sp or sp2 orbitals.
- BOrbital overlap in a bond is greater than that in a bond.
- CThe triple bond is weakened by s-p mixing.
- DRepulsion between the three pairs of bonding electrons reduces the energy of the triple bond.
- EThe triple bond is weakened by electrons occupying an antibonding orbital.
Which of the following electronic transitions do alkanes exhibit?
- A to
- B to
- C to
Liquid oxygen is attracted by a magnetic field. Which feature of the molecule is responsible for this behavior?
- AUnpaired electrons in antibonding orbitals
- BPaired electrons in antibonding orbitals
- CPaired electrons in nonbonding orbitals
- DUnpaired electrons in nonbonding orbitals
- EUnpaired electrons in bonding orbitals
Which of the following statements is true about nonbonding molecular orbitals?
- AThey help hold the molecule together, once it is formed.
- BThey counteract bond formation in a molecule.
- CThey are similar in energy to the atomic orbitals.
- DThey are responsible for the formation of bonds.
- EThey are responsible for the formation of bonds.
According to valence bond theory (VBT), has no unpaired electrons. MO theory shows two unpaired electrons in a molecular orbital. Which of the following experiments supports the correct electron configuration?
- AThere is no way to know which theory is correct.
- BAn EPR spectrum shows that oxygen is paramagnetic; VBT is correct.
- CAn EPR spectrum shows that oxygen is paramagnetic; MO theory is correct.
- DInfrared spectroscopy shows a double-bond stretch; VBT is correct.
- EInfrared spectroscopy shows a double-bond stretch; MO theory is correct.