Question 1

Which of the following statements best explains why O$$_2 is $$paramagnetic, even though its Lewis structure predicts it should be diamagnetic?

Accepted Answer

Because O$$_2$$ has unpaired electrons in its antibonding molecular orbitals, as predicted by molecular orbital theory.

Question 2

According to valence bond theory, what is a chemical bond?

Accepted Answer

The overlap between half-filled atomic orbitals on two atoms.

Question 3

How many hybrid orbitals are formed when one s and three p orbitals are hybridized?

Accepted Answer

$$4$$

Question 4

Which type of bond allows for free rotation around the bond axis without breaking the bond?

Accepted Answer

Sigma ($$\sigma) $$bond

Question 5

Why is a double bond not simply twice as strong as a single bond, according to valence bond theory?

Accepted Answer

Because a double bond consists of one sigma ($$\sigma) $$and one pi ($$\pi) $$bond, and the pi bond is weaker than the sigma bond.

Question 6

What is the hybridization of the central atom in a molecule with a trigonal bipyramidal electron geometry?

Accepted Answer

$$sp^3d$

Question 7

Which of the following best describes a pi ($$\pi) $$bond?

Accepted Answer

A bond formed by the sideways overlap of unhybridized p orbitals, with electron density above and below the internuclear axis.

Question 8

What is the bond order for a diatomic molecule with six electrons in bonding molecular orbitals and three electrons in antibonding molecular orbitals?

Accepted Answer

$$1.5$$

Question 9

Which of the following statements about molecular orbital (MO) theory is correct?

Accepted Answer

Electrons in bonding MOs are stabilizing, while electrons in antibonding MOs are destabilizing.

Question 10

A molecule has four electron groups around its central atom. What is the expected hybridization and geometry?

Accepted Answer

$$sp^3$$ hybridization and tetrahedral geometry

Question 11

Which of the following molecules or ions is predicted to be paramagnetic based on its molecular orbital diagram?

Accepted Answer

O$$_2$$

Question 12

What is the bond order of the H$$_2^+$$ ion?

Accepted Answer

$$0.5$$

Question 13

Which of the following best describes the process of hybridization?

Accepted Answer

Mixing different types of atomic orbitals in the valence shell to form a new set of degenerate orbitals.

Question 14

Which hybridization is expected for the central atom in SF$$_6$$?

Accepted Answer

$$sp^3d^2$

Question 15

According to molecular orbital theory, why does the He$$_2$$ molecule not exist?

Accepted Answer

Because the bond order is zero, indicating no net bonding.

Question 16

Which of the following is a limitation of valence bond theory?

Accepted Answer

It does not predict the correct magnetic behavior of molecules like O$$_2.$$

Question 17

What is the bond order of N$$_2^-$$ according to molecular orbital theory?

Accepted Answer

$$2.5$$

Question 18

Which of the following best describes a chemical bond according to molecular orbital theory?

Accepted Answer

Atoms bond when electrons can lower their energy by occupying molecular orbitals of the molecule.

Question 19

Which of the following statements about hybrid orbitals is correct?

Accepted Answer

The number of hybrid orbitals formed equals the number of atomic orbitals combined.

Question 20

A molecule has three electron groups around its central atom. What is the expected hybridization and geometry?

Accepted Answer

$$sp^2$$ hybridization and trigonal planar geometry

Chemical Bonding II: Valence Bond and Molecular Orbital Theory – Study Notes

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