(e) Dishwashing liquid molecules must attract water molecules better than they attract each other because water dissolves
the substance and washes it away. Gear oil molecules must attract each other better than they attract water molecules—because water doesn’t dissolve the oil or wash it away.
(f) We observe that the dishwashing liquid will mix with (dissolve) the oil, and the mixture (solution) of the two will
dissolve in water, and be washed away. It seems that dishwashing liquid molecules are somehow able to attract both
water molecules and oil molecules.
(g) Dishwasher detergent is thick and viscous, so its molecules are quite cohesive, and seem to be adhesive to glass and
water and oil. Gear oil molecules are less cohesive, and not very adhesive to glass or water—only to the dishwashing
liquid. This seems logical, since dishwashing liquids are designed to attract and dissolve all kinds of food materials;
and gear oil is designed to make metal surfaces slide against each other without wearing down.
4.1 LEWIS THEORY OF BONDING
PRACTICE
(Page 227)
Understanding Concepts
1. (a) Mg - 2, Cl - 1
(b) C - 4, H - 1
(c) H -1, O - 2
(d) H - 2, S - 2
(e) N - 3, H - 1
2. In the order that they were created by chemists, we have the (c) Dalton atom, (b) empirical formulas, (d) Kekulé structures, (a) Lewis structures, and (e) Schrödinger quantum mechanics.
3. (a) 1s2 2s2 2p6 3s2 3p1
Al
(b) 1s2 2s2 2p6 3s2 3p5
Cl
(c) 1s2 2s2 2p6 3s2 3p6 4s2
Ca
(d) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p2 Ge
4. (a)
O
(b)
P
(c)
Br
(d) Rb
5. (a)
H
H
H C H
H
H
C
H
H
(b)
O H
H
O
H
H
Copyright © 2003 Nelson
Chemical Bonding
111
(c)
O C O
(d)
S H
H
O
S
C
O
H
H
(e) H N H
H
H
N
H
H
Applying Inquiry Skills
6. A new scientific concept must explain existing evidence, and should predict new observations successfully, before it
is generally accepted by the scientific community.
7. Decompose a known mass of a pure compound. Identify and measure the masses of the products produced.
Extension
8. Kekulé structures simply showed which atoms were bonded to which, while Lewis structures explain the bonding in
terms of electron arrangement.
9. Were Lewis structures derived from quantum theory? Lewis himself said not, and has a body of notes to support this.
Others say the parallels with Sommerfeld’s work on electron energy sublevels are too great to be due to coincidence.
The truth probably lies between, since this was long past any time where scientists worked isolated from knowledge
of the work of others.
PRACTICE
(Page 229)
Understanding Concepts
10. (a)
_
O
O Cl O
32 e – total
O
(d)
(g)
112
N O
Chapter 4
8 e – total
+
2
O
C
O
(e)
+
H O H
H
(b)
(c)
_
_
10 e – total
C N
24 e – total
O
_
O H
C
O O
(f)
24 e – total
_
O H
N
O O
24 e – total
10 e – total
Copyright © 2003 Nelson
Applying Inquiry Skills
11. (a) NH3(g) HCl(g) → NH4Cl(s)
(b)
H
H N H + H Cl
H N H
H
H
H
+
–
Cl
(c) Test the solubility of the product in water. Measure the electrical conductivity of the aqueous solution and add a
few crystals of silver nitrate to test for the presence of chloride ions by precipitating silver chloride.
F
S C
l
P
F
Cl
Cl
F
(c)
F
(b)
Cl
Extension
12. (a)
F Cl F
F
F
SECTION 4.1 QUESTIONS
(Page 230)
Understanding Concepts
1. The Dalton atom concept made it possible to express chemical composition of compounds as empirical formulas. The
later development of electron energy levels in the Bohr atom concept made it possible for Lewis diagrams to show
how valence electron rearrangement is involved in reactions.
Be
2. (a) 1s2 2s2
(b) 1s2 2s2 2p6 3s2 3p3
P
(c) 1s2 2s2 2p6 3s2
Mg
(d) 1s2 2s2 2p4
O
3. (a)
F
(b)
Al
(c)
Br
(d)
Sr
4. (a)
S H
H
S
(b)
H
Cl
Cl
Cl C Cl
Cl
H
Cl
C
Cl
Cl
(c)
Cl N Cl
Cl
Cl
N
Cl
Cl
(d)
O
O S O
O
2
2
O
_
O
S
_
O
O
Copyright © 2003 Nelson
Chemical Bonding
113
(e)
O
O S O
O H
(g)
_
O
_
O
C O
C
S
O
O
H
_
(f)
_
N
O
N
O
(h)
O
O
O P O
O
O
O
3
3
O
_
O
P
_
O
O
Extensions
5. (a) BCl3(g) NH3(g) → BCl3NH3
(b)
Cl H
Cl
B N H
+
H
N
H
Cl
B
Cl Cl
Cl H
H
6. (a)
+
H
H N H
H
–
Cl
(b) The compound is easy to represent with Lewis structures once you accept the idea of ammonium as a polyatomic
positive ion, with nitrogen able to bond four times to hydrogen if an electron is removed.
4.2
THE NATURE OF THE CHEMICAL BOND
PRACTICE
(Page 232)
Understanding Concepts
1. A helium atom has a single orbital containing a pair of electrons. Generally, two half-filled orbitals overlap to form a
bond.
2. An orbital formed from overlap of two atomic orbitals is like an individual atomic orbital in that it is full when two
paired electrons occupy it.
3. This overlap is not possible because it would include three electrons occupying one shared orbital.
4. (a)
H
Cl
1s and 2p orbitals
(b)
Cl
Cl
2p and 2p orbitals
114
Chapter 4
Copyright © 2003 Nelson