Compounds and Their Bonds
Valence Electrons
Ions and the Octet Rule
Chemical Bonds
 Attraction between two or more atoms
 Interaction between valence electrons
 Ionic bonds
 Covalent bonds
Valence Electrons
 Electrons in the highest (outer) electron level
 Have most contact with other atoms
 Known as valence electrons
 Outer shelI of noble gases the outer shell
contains 8 valence electrons (except He = 2)
Example:
Ne
2, 8
Ar
2, 8, 8
Electron Dot Structures
Symbols of atoms with dots to represent the
valence-shell electrons
1A
2A
3A
4A
5A
6A
7A
H
Li
8A
He:



Be
B 

C


Na Mg



Al
 Si 



N


O :F



P

S






: Ne :


: Cl  : Ar :


Electron Dot Formulas

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
3) P
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
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
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 1 metals 
ion 1+
Group 2 metals 
ion 2+
Group 3 metals 
ion 3+
Formation of Sodium Ion
Sodium atom
Na 
2-8-1
11 p+
11 e0
– e
Sodium ion

Na +
2-8 ( = Ne)
11 p+
10 e1+
Formation of Magnesium Ion
Magnesium atom
Magnesium ion

Mg 
2-8-2
12 p+
12 e0
– 2e

Mg2+
2-8 (=Ne)
12 p+
10 e2+
Some Typical Ions with
Positive Charges (Cations)
Group 1
Group 2
Group 3
H+
Mg2+
Al3+
Li+
Ca2+
Na+
Sr2+
K+
Ba2+
Octet Rule Understanding
A. Number of valence electrons in aluminum
1) 1 e2) 2 e3) 3 eB.
Change in electrons for octet
1) lose 3e2) gain 3 e- 3) gain 5 e-
C.
Ionic charge of aluminum
1) 32) 5-
3) 3+
Solution
A. Number of valence electrons in aluminum
3)
3 eB.
Change in electrons for octet
1)
lose 3e-
C.
Ionic charge of aluminum
3) 3+
Ion Charges
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-
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) 3-
More Octet Rule
A. Why does Ca form a Ca2+ ion?
B. Why does O form O2- ion?
Solution
A. Why does Ca form a Ca2+ ion?
Loses 2 electrons to give octet
2-8-8-2
2-8-8 (like Ar, isoelectronic)
B.
Why does O form O2- ion?
Gains 2 electrons to give octet
2-6 + 2e2-8 (like Ne, isoelectronic)
Ions from Nonmetal Ions
In ionic compounds, nonmetals in 15, 16,
and 17 gain electrons from metals
Nonmetal add electrons to achieve the octet
arrangement
Nonmetal ionic charge:
3-, 2-, or 1-
Fluoride Ion
unpaired electron

:F

2-7
9 p+
9 e0
+ e
octet

1-
: F:

2-8 (= Ne)
9 p+
10 e1ionic charge
Octet Rule & Nomenclature
Complete the names of the following ions:
15
16
17
N3
O2
F
nitride
__________
fluoride
P3
___________
S2
__________
Cl
_________
Br 
_________
Solution
15
16
17
N3
O2
F
oxide
fluoride
S2
Cl
sulfide
chloride
nitride
P3
phosphide
Br 
bromide