Covalent Bonds and
Compounds
Molecules
Three Kinds of Bonds
1.
2.
3.
Non-metal to non-metal
metal to non-metal
metal to metal



Covalent
Ionic
Metallic
Why do atoms bond?
To achieve stability
 Stability is achieved when octet rule is
satisfied

Bonds and Electronegativity
Electrons are transferred between atoms
when the difference in electronegativity
between the atoms is quite high.
 The amount of transfer depends on the
electronegativity difference.

Bonds and Electronegativity
The number 1.67 seems to be the magic
number.(Note:1.67 rounds to 1.7)
 If the electronegativity difference is less
than 1.67, the bond is more covalent than
ionic.
 If the electronegativity difference is greater
than 1.67, the bond is more ionic than
covalent.
 Pg. 263 Figure 9-15

Electronegativity Difference
Covalent < 1.67
However –
 0 -.3 is non-polar covalent
 . 3 – 1.67 polar covalent
 There are 7 instances of perfectly covalent
bonds (electronegativity difference = 0)
 H2, N2, O2, F2, Cl2, Br2, I2

Practice problems 22

Pg. 266
What is a covalent bond?
Bond that results from the sharing of
electons between nonmetals
 Type of bonding found in majority of
known compounds
 Molecule – formed when two or more
atoms bond covalently
***Ex. of molecules – carbohydrates,
proteins, fats, DNA, wool, cotton, and
synthetic fibers found in clothes you wear
all consist of molecules

Lewis structures
Use electron dot diagrams or Lewis dot
diagrams to show how electrons are
arranged in molecules
 Ex. HBr
 Pg. 244 practice problems 19 use different
colors for different atoms

Covalent bonds
Lewis structures
 Single covalent bonds – single pair of
electrons shared
 Double covalent bond - sharing of two
pairs of electrons
 Triple bond – sharing of 3 pairs of
electrons

Nomenclature (naming)

Covalent bonds are generally between two
non-metals.
 CO - Carbon monoxide
 CO2 - Carbon dioxide
Prefixes









1
2
3
4
5
6
7
8
9
-
-
-
Mon(o)
Di
Tri
Tetr(a)
Pent(a)
Hex(a)
Hept(a)
Oct
Non
Nitrogen and oxygen
(five molecules)





N2O
NO
N2O3
NO2
N2O5
-
Dinitrogen monoxide
Nitrogen monoxide
Dinitrogen trioxide
Nitrogen dioxide
Dinitrogen pentoxide
Metallic Bonds
Bonding in metals is due to delocalized
electrons.
 These often exist in what is called a sea of
electrons.

Sea of “delocalized” electrons
Metal atoms
Metallic Bonds
This explains many of the properties of
metals:
 Malleable
 Ductile
 Conducts electricity well

Alloys

Two Metals (and sometimes other
substances) bonded (mixed) together.
Alloys

Two Metals (and sometimes other
substances) bonded (mixed) together.
Alloys

Two Metals (and sometimes other
substances) bonded (mixed) together.
Alloys

Two Metals (and sometimes other
substances) bonded (mixed) together.