Answers to Practice Questions Chapter 1

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



  • Identify 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 N2 molecule: ""


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


Because the formal charges are not minimized in 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 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 azide anion, N3, and indicate the most stable one.



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






  • What is the hybridization of oxygen atom in H2O molecule?
four electron groups around central oxygen (2 BP, 2LP), the oxygen is in sp3 hybridization
  • What is the hybridization of xenon atom in XeF4 molecule, and what is the shape of the whole molecule?
six electron groups around central oxygen (4 BP, 2 LP), the oxygen is in sp3d2 hybridization


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