Center for Academic Services & Advising
November 19, 2015
Chemistry I
1. Write the Lewis symbols that represent the ions in each ionic compound:
a. SrO
b. Li2S
c. CaI2
CSI Worksheet 10
d. RbF
2. Use covalent Lewis structure to show why nitrogen and hydrogen form NH3 and why NH2 and NH4 are
unstable.
When three hydrogens are present N has a stable octet. With 2 hydrogens, N only has 7
electrons. With 4 hydrogens N has 9 electrons
3. Write the Lewis structure for each molecule:
a. NF3
b. HBr
c. SBr2
d. CCl4
4. Write the Lewis structure for each molecule or ion:
a. H3COH
b. CNc. NO2-
d. ClO-
5. In N2O, nitrogen is the central atom and the oxygen atom is terminal. In OF2, however, O is the central
atom. Use formal charges to explain why.
COLORADO SCHOOL OF MINES
Frances I Core Supplemental Instruction Facilitator | Chemistry II
Center for Academic Services & Advising
Atom
# Valence electrons
I
N
5
II
O
6
III
O
6
IV
F
7
# lone pairs
0.5 (number of bonding electons)
0
4
0
4
4
4
4
2
Formal Charge
+1
+2
0
+1
It’s better to have a positive charge on a less electronegative atom.
6. Draw the Lewis structure (including resonance structures) for methyl azide (CH3N3). For each resonance
structure, assign formal charges to all atoms that have a formal charge.
Atom
# V.E
# lone p
0.5 bond
F.C
Left Structure
N left
N middle
5
5
4
0
2
4
-1
+1
N Right
5
2
3
0
Middle Structure
N Left
N middle
5
5
2
0
3
4
0
+1
N right
5
4
2
-1
Right Structure
N left
N middle
5
5
6
0
1
4
-2
+1
N right
5
0
4
+1
7. Draw the Lewis structure for each organic compound from its condensed structural formula:
a. C3H8
b. CH3OCH3
c. CH3COCH3
d. CH3COOH
e. CH3CHO
COLORADO SCHOOL OF MINES
Frances I Core Supplemental Instruction Facilitator | Chemistry II