Question 1

Which of the following statements best explains why the Lewis structure of O$$_2$$ incorrectly predicts its magnetic properties?

Accepted Answer

Lewis theory does not account for the delocalization of electrons, which is necessary to explain O$$_2$$'s paramagnetism.

Question 2

According to valence bond theory, what is the main reason for the formation of a chemical bond between two hydrogen atoms?

Accepted Answer

The overlap of two half-filled 1s atomic orbitals, resulting in a pair of spin-paired electrons.

Question 3

Which hybridization scheme is used by the central atom in SF$$_6$$?

Accepted Answer

$$sp^3d^2$

Question 4

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

Accepted Answer

$$\frac{1}{2}(8-3) = 2.5$$

Question 5

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

Accepted Answer

N$$_2$$

Question 6

Why is the bond angle in methane (CH$$_4) $$observed to be 109.5$$^	ext{o}$$ instead of 90$$^	ext{o} as $$predicted by unhybridized orbitals?

Accepted Answer

The carbon atom undergoes $$sp^3$$ hybridization, resulting in four equivalent orbitals oriented tetrahedrally.

Question 7

Which of the following best describes the difference between a sigma ($$\sigma) $$bond and a pi ($$\pi) $$bond?

Accepted Answer

A $$\sigma$$ bond results from end-to-end overlap of orbitals, while a $$\pi$$ bond results from side-to-side overlap of unhybridized p orbitals.

Question 8

Which of the following molecules has a bond order of zero and is therefore not stable according to molecular orbital theory?

Accepted Answer

Be$$_2$$

Question 9

What is the hybridization of the central atom in BrF$$_3$$?

Accepted Answer

$$sp^3d$

Question 10

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 11

Which of the following best explains why rotation around a double bond is restricted?

Accepted Answer

The presence of a $$\pi$$ bond, formed by side-to-side overlap of p orbitals, prevents free rotation.

Question 12

Which of the following is true about the bond order and stability of the He$$_2$$ molecule?

Accepted Answer

Bond order is zero, so He$$_2 is $$not stable.

Question 13

Which of the following best describes the hybridization and geometry of the central atom in PF$$_5$$?

Accepted Answer

$$sp^3d$ hybridization and trigonal bipyramidal geometry

Question 14

Which of the following molecules contains both $$\sigma$$ and $$\pi$$ bonds?

Accepted Answer

C$$_2H$_4 ($$ethylene)

Question 15

In the MO diagram for NO, which atom's atomic orbitals contribute more to the bonding molecular orbitals?

Accepted Answer

The more electronegative atom (Oxygen)

Question 16

Which of the following is a consequence of electron delocalization in benzene according to molecular orbital theory?

Accepted Answer

Benzene is more stable than predicted by Lewis or valence bond theory.

Question 17

Which of the following best describes the bond order in O$$_2$$ according to molecular orbital theory?

Accepted Answer

$$\frac{1}{2}(8-4) = 2$$

Question 18

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 19

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

Accepted Answer

O$$_2$$

Chemical Bonding II: Valence Bond Theory and Molecular Orbital Theory

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