Question

1. Predict which of the following molecules will have a stronger ionic bond. (Think about charges and
bond lengths!)
a) MgBr2 or MgF2
b) Na2O or Rb2O
c) Ca3(PO4)2 or Li3PO4
2. Determine the number of valence electrons in each molecule below.
a) C4H10O
b) CH3NO2
c) POCl2-1
d) HBrO3
3. Draw full Lewis structures for the following molecules. Indicate formal charges and resonance
structures, as appropriate.
a) IO3-
b) SF4
c) SOCl2
d) dinitrogen monoxide (laughing gas), N – N – O.
4. Draw the Lewis structure for Nitryl chloride, NO2Cl. Nitrogen is the central atom, and is surrounded
by both oxygens and the chlorine separately. Include formal charges and resonance structures,
where necessary. Are the two N-O bonds the same length? Why or why not?
5. Draw Lewis structures for NO2+ and NO2-. Which molecule has the shorter average N – O bond
length?

Answer 1

1. Ionic bond strength depends on two things:
i) ionic charge - the greater the product of the ionic charges the stronger the bond
ii) ionic size - the lower the sum of the anion and cation radii, the stronger the bond

a) MgF₂ > MgBr₂ (Bond length will be more in MgBr₂ which will reduce the strength of bond)

b) Na₂O > Rb₂O (Bond length will be more in MgBr₂ which will reduce the strength of bond)

c) Ca₃(PO₄)₂ > Li₂PO₄ (Ionic charge in Ca²⁺ increases the ionic bond strength as compared to Li⁺)

2. a) C₄H₁₀O - Valence electrons = 4 x 4 + 10 x 1 + 6 = 32

b) CH₃NO₂ - Valence electrons = 4 + 3 + 5 + 6 x 2 = 24

c) POCl₂^- - Valence electrons = 5 + 6 + 2 x 7 + 1 = 26

d) HBrO₃ - Valence electrons = 1 + 7 + 3 x 6 = 26

3.

a) IO₃^-

b) SF₄

c) SOCl₂

d) Dinitrogen Monoxide (N-N-O)

4. NO₂Cl