Practice Problems:
Bonding and Lewis Dot Structures
CHEM 1A
1. Calculate the difference in electronegativities for the following atoms, and state whether a bond
between them would be ionic, polar covalent, or non-polar covalent.
Difference in EN
Type of Bond
a) Na & F
b) H & O
c) N & Br
d) Mg & O
2. What two factors influence whether or not a molecule will be polar overall?
1)
2)
3. Give the valence level orbital notation and draw the Lewis dot structure for each of the following
neutral atoms and simple ions.
a) N
b) S
c) Ca2+
d) Se2–
4. Draw Lewis dot structures for the following molecules:



Using VSEPR theory, predict the molecular shape and bond angle
State whether the molecule is polar or non-polar overall
If the molecule is polar overall, show the appropriate partial charges (+ and –) on polar bonds
a) CH4
b) CH2O
c) H2O
d) NH3
5. Draw Lewis dot structures for the following polyatomic ions:



Show resonance structures where appropriate
Using VSEPR theory, predict the shape and bond angle
Include formal charges in at least one of the structures
a) NH4+
b) CO32–
c) NO2–
d) CN–
6. Three non-equivalent Lewis dot structures are shown below for the polyatomic ion thiocyanate
(SCN–).
a) Assign a formal charge to each of the atoms. The equation for calculating formal charge should
be shown, but work is not required for each.
b) Which one of the possible structures for SCN– shown would contribute the LEAST to the overall
structure? Explain why.
c) Of the two remaining structures, which structure is likely to contribute MOST to the overall
structure of SCN–? Explain why.