Question 1

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

Accepted Answer

Sigma bonds are stronger than pi bonds because they result from head-on overlap, while pi bonds are weaker due to side-to-side overlap.

Question 2

How many sigma ($$\sigma) $$and pi ($$\pi) $$bonds are present in a molecule of nitrogen gas ($$\mathrm{N_2$}$$)?

Accepted Answer

One $$\sigma$$ bond and two $$\pi$$ bonds

Question 3

Which hybridization corresponds to a central atom with three electron domains?

Accepted Answer

$$sp^2$$

Question 4

What is the molecular geometry of a molecule with four electron domains and one lone pair on the central atom?

Accepted Answer

Trigonal pyramidal

Question 5

In the context of molecular orbital (MO) theory, what is the bond order of $$\mathrm{O_2$}$$?

Accepted Answer

$$2$$

Question 6

Which of the following best explains why $$\mathrm{He_2$}$$ does not exist as a stable molecule?

Accepted Answer

The bond order is zero because the number of electrons in bonding and antibonding orbitals is equal.

Question 7

Which of the following molecules contains an atom with $$sp^3$$ hybridization?

Accepted Answer

$$\mathrm{CH_4$}$$

Question 8

A molecule has a central atom with two double bonds and no lone pairs. What is the hybridization of the central atom?

Accepted Answer

$$sp$$

Question 9

Which of the following statements about molecular orbitals is correct?

Accepted Answer

Bonding molecular orbitals are lower in energy than the atomic orbitals from which they are formed.

Question 10

Which of the following best describes the concept of resonance in molecular orbital theory?

Accepted Answer

Resonance is explained by the delocalization of electrons in molecular orbitals formed from p orbitals.

Question 11

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

Accepted Answer

$$\mathrm{O_2$}$$

Question 12

What is the bond order of $$\mathrm{C_2$^{2+}}$$ based on its molecular orbital diagram?

Accepted Answer

$$1$$

Question 13

Which of the following best describes the role of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) in chemical reactions?

Accepted Answer

Reactions occur when electrons move from the HOMO of one molecule to the LUMO of another.

Question 14

Which of the following statements about hybridization is correct?

Accepted Answer

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

Question 15

A molecule has a central atom with three bonding pairs and one lone pair. What is the electron geometry and hybridization of the central atom?

Accepted Answer

Tetrahedral, $$sp^3$$

Question 16

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

Accepted Answer

$$\mathrm{O_2$}$$

Question 17

Which of the following best explains why the bond order of $$\mathrm{O_2$^{2+}} is $$greater than that of $$\mathrm{O_2$}$$?

Accepted Answer

$$\mathrm{O_2$^{2+}}$$ has fewer electrons in antibonding orbitals.

Question 18

Which of the following is a consequence of s-p mixing in molecular orbital diagrams for period 2 diatomic molecules?

Accepted Answer

The $$\pi_{2p}$$ orbitals are lower in energy than the $$\sigma_{2p}$$ orbital for B$$_2$$, C$$_2$$, and N$$_2.$$

Question 19

Which of the following statements about bond length and bond order is correct?

Accepted Answer

A higher bond order corresponds to a shorter bond length.

Question 20

In the molecule shown below (see image with aromatic ring and side chains), what is the hybridization of the nitrogen atom in the side chain?

Accepted Answer

$$sp^3$$

Valence Bond Theory, Hybridization, and Molecular Orbital Theory: Study Notes

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