Answers to Chapter 1 Practice Questions

1.1 Number of valence electrons:

B: 3 valence electrons

N: 5 valence electrons

O: 6 valence electrons

Cl: 7 valence electrons

Mg: 2 valence electrons

1.2

• Identify whether the following bond is “polar” or “non-polar”.

C-C: non-polar            C-H: non-polar (very close electronegativity for C and H)

 B-F: polar                   O-O: non-polar              C=N: polar

• Rank the following bonds in the order of increasing bonding polarity: C—S, C—O, C—F (referring to the trend of EN, no need to use the exact EN values).

bonding polarity: C—S < C—O < C—F

1.3  Draw the Lewis structure of an N₂ molecule:

1.4 Why is the following structure is not the best way to show the Lewis structure of CO₂?

Because the formal charges are not minimized in the above structure. The formal charge in the best Lewis structure of CO₂ are all zero, and the best Lewis structure of CO₂ is shown here:

1.5 Draw all the equivalent resonance structures for the following species. Include any non-zero formal charges in the structures.

• O₃ molecule

• nitrate anion NO₃^–

• chlorate anion ClO₃^–

1.6 Draw all the resonance structures for the azide anion, N₃^–, and indicate the most stable one.

1.7 Draw a new resonance structure and compare the relative stability; show the arrows in the original structure.

1.8

• What is the hybridization of the oxygen atom in a H₂O molecule?

• What is the hybridization of the xenon atom in an XeF₄ molecule, and what is the shape of the whole molecule?