Chapter 4
Compounds and Their Bonds
4.1 Valence Electrons
4.2 Octet Rule and Ions
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Chemical Bonds
 Attraction between two or more atoms
 Interaction between valence electrons
 Ionic bonds
 Covalent bonds
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Valence Electrons
 Electrons in the highest (outer) electron level
 Have most contact with other atoms
 Known as valence electrons
 Outer shells of noble gases contain 8 valence
electrons (except He = 2)
Example:
Ne
2, 8
Ar
2, 8, 8
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Electron Dot Structures
Symbols of atoms with dots to represent the valence-shell
electrons
1A
2A
3A
4A
5A
6A
7A
8A
H
He:

Li Be


B 


C


Na Mg

N



O





 Al
 Si 
P
 S

 Timberlake

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

: F  :Ne :




:Cl  :Ar :


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Learning Check

A.
X would be the electron dot formula for
1) Na
B.

X

1) B
2) K
3) Al
would be the electron dot formula
2) N
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3) P
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Solution

A.
X would be the electron dot formula for
1) Na
B.

X

2) N
2) K
would be the electron dot formula
3) P
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Octet Rule
 An octet in the outer shell makes atoms stable
 Electrons are lost, gained or shared to form an octet
 Unpaired valence electrons strongly influence
bonding
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Formation of Ions from Metals
 Ionic compounds result when metals react with
nonmetals
 Metals lose electrons to match the number of valence
electrons of their nearest noble gas
 Positive ions form when the number of electrons are
less than the number of protons
Group 1A metals  ion 1+
Group 2A metals  ion 2+
•
Group 3A metals  ion 3+
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Formation of Sodium Ion
Sodium atom
Na 
– e
Sodium ion

Na +
2-8-1
11 p+
11 e0
2-8 ( = Ne)
11 p+
10 e1+
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Formation of Magnesium Ion
Magnesium atom
Magnesium ion

Mg 
– 2e

2-8-2
12 p+
12 e0
Mg2+
2-8 (=Ne)
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12 p+
10 e2+
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Some Typical Ions with Positive
Charges (Cations)
Group 1A
Group 2A
Group 3A
H+
Mg2+
Al3+
Li+
Ca2+
Na+
Sr2+
K+
Ba2+
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Learning Check
A. Number of valence electrons in aluminum
1) 1 e2) 2 e3) 3 e-
B.
C.
Change in electrons for octet
1) lose 3e2) gain 3 eIonic charge of aluminum
1) 32) 5LecturePLUS Timberlake
3) gain 5 e-
3) 3+
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Solution
A. Number of valence electrons in aluminum
3)
3 e-
B.
Change in electrons for octet
1)
lose 3e-
C.
Ionic charge of aluminum
3) 3+
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Learning Check
Give the ionic charge for each of the following:
A. 12 p+ and 10 e1) 0
2) 2+
3) 2B. 50p+ and 46 e1) 2+
2) 4+
3) 4-
C. 15 p+ and 18e2) 3+
2) 3-
3) 5-
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Solution
Give the ionic charge for each of the following:
A. 12 p+ and 10 e2) 2+
B. 50p+ and 46 e2) 4+
C. 15 p+ and 18e2) 3LecturePLUS Timberlake
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Learning Check
A. Why does Ca form a Ca2+ ion?
B. Why does O form O2- ion?
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Solution
A. Why does Ca form a Ca2+ ion?
Loses 2 electrons to give octet
2-8-8-2
2-8-8 (like Ar)
B.
Why does O form O2- ion?
Gains 2 electrons to give octet
2-6 + 2e2-8 (like Ne)
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Ions from Nonmetal Ions
In ionic compounds, nonmetals in 5A, 6A, and 7A
gain electrons from metals
Nonmetal add electrons to achieve the octet
arrangement
Nonmetal ionic charge:
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Fluoride Ion
unpaired electron

:F
octet

+ e
: F:


2-7
9 p+
9 e0
1-
2-8 (= Ne)
9 p+
10 e1ionic charge
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Learning Check
Complete the names of the following ions:
5A
6A
7A
N3
O2
F
nitride
__________
fluoride
P3
S2
___________ __________
Cl
_________
Br 
_________
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Solution
5A
6A
7A
N3
O2
F
oxide
fluoride
S2
Cl
sulfide
chloride
nitride
P3
phosphide
Br 
bromide
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