$$\text{Bond order} = \frac{1}{2}[(\text{number of electrons in bonding MOs}) - (\text{number of electrons in antibonding MOs})]$$

Question 1

Which of the following statements best explains why Lewis theory fails to predict the paramagnetism of O$$_2$$?

Accepted Answer

Lewis theory does not account for the delocalization of electrons across the molecule.

Question 2

According to valence bond theory, what is required for a chemical bond to form between two atoms?

Accepted Answer

The overlap of two half-filled orbitals with opposite spins.

Question 3

Which type of bond is formed by the side-by-side overlap of two p orbitals?

Accepted Answer

A pi ($$\pi) $$bond

Question 4

What is the hybridization of the central atom in methane (CH$$_4$$)?

Accepted Answer

$$sp^3$$

Question 5

A molecule has a trigonal planar geometry. What is the expected hybridization of the central atom?

Accepted Answer

$$sp^2$$

Question 6

Which of the following molecules is predicted to have $$sp^3d^2$ hybridization on the central atom?

Accepted Answer

SF$$_6$$

Question 7

Which statement about bond rotation is correct?

Accepted Answer

Rotation around a single ($$\sigma) $$bond is generally allowed without breaking the bond.

Question 8

How many $$\sigma$$ and $$\pi$$ bonds are present in a molecule of ethyne (C$$_2H$_2$$)?

Accepted Answer

3 $$\sigma$$ bonds and 2 $$\pi$$ bonds

Question 9

Which of the following best describes the bond order formula in molecular orbital theory?

Accepted Answer

$$	ext{Bond order} = \frac{1}{2}[(	ext{number of electrons in bonding MOs}) - (	ext{number of electrons in antibonding MOs})]$$

Question 10

Why does the molecule He$$_2$$ not exist according to molecular orbital theory?

Accepted Answer

The bond order is zero, so the molecule is not stable.

Question 11

Which molecule 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 hybridization scheme is associated with a linear electron geometry and a bond angle of $$180^\circ$$?

Accepted Answer

$$sp$$

Question 14

In the molecule BrF$$_3$$, what is the hybridization of the central atom?

Accepted Answer

$$sp^3d$

Question 15

Which of the following best explains why double bonds restrict rotation in molecules?

Accepted Answer

The $$\pi$$ bond formed by side-by-side overlap prevents rotation without breaking the bond.

Question 16

Which of the following molecules has a central atom with $$sp^2$$ hybridization?

Accepted Answer

CH$$_2O$$

Question 17

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

Accepted Answer

Octahedral, $$sp^3d^2$

Question 18

Which of the following is a correct statement about molecular orbitals?

Accepted Answer

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

Question 19

For the N$$_2^-$$ ion, what is the bond order and magnetic property predicted by molecular orbital theory?

Accepted Answer

Bond order = $$2.5$$, paramagnetic

Chemical Bonding II: Valence Bond Theory, Hybridization, and Molecular Orbital Theory

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