Chapter 6 Molecular Structure & Bonding
Example 6.6 Describe the bonding in and the structure of the following ions: a) Bromate ion, BrO
1-^3
The Lewis structure of the br
omate ion shows four electron
regions around the bromine
atom, so it is sp
3 hybridized. The three O atoms form the base of this trigonal pyramidal
ion. All BrO
1- 3
bonds are single bo
nds and, therefore,
σ bonds. The O-Br-O bond angles
are ~109
o. The negative charge of the ion is distri
buted equally over all of the oxygen
atoms. The ball-and-stick and space-filli
ng models are shown in the margin.
BrO
1- 3
ion
NO
1- ion 3
SO
2- 4
ion
OBr
O
O
+2
+2 Br
O
OO
b) Nitrate ion, NO
1- 3
The Lewis structure of NO
1- has three electron groups around the nitrogen, so it is sp 3
2
hybridized and the ion is planar. The
bond is shared by all three N-O bonds, which are π
equivalent with bond orders of
4 /^3
(four shared pairs spread equally over three bonding
regions). The O-N-O bond angles are all 120
o. Resonance places the negative formal
charge equally on all of the oxygens. Posi
tively charged species bond to one of the
oxygens but not to the nitrogen. For example, addition of H
1+ to NO
1- 3
results in HNO
, 3
nitric acid, which contains an O-H bond, not an N-H bond.
O N
OO
ON
O
O
c) Sulfate ion, SO
2- 4
The Lewis structure of the su
lfate ion indicates four elec
tron regions around the sulfur
atom, so the sulfur is sp
3 hybridized. The sulfate ion is tetrahedral. The S-O bonds are all
single bonds (that is,
bonds). The O-S-O bond angles are all 109σ
o. The negative charge
on the ion is distributed equally among the ox
ygens. Note that the sum of the formal
charges is -2, the charge on the io
n. When the sulfate ion bonds to H
1+ ions to form
covalent bonds, it does so through the oxygen atoms. Thus, sulfuric acid (H
SO 2
) has two 4
O-H bonds.
OS
O
O
O
O
O
S
OO
+2
+2
© by
North
Carolina
State
University