Covalent Bonding
Forming Molecular Bonds
What is a covalent bond?

 The chemical bond that results from the sharing of
electrons
 Non-metals combine to acquire a full valence shell of
8 valence electrons
 Example:
7 valence e-
8 valence e-
Degree of sharing

Non-polar Covalent
e-
are
shared
equally
Polar Covalent
e-
shared
unequally
Ionic
one
atom
takes efrom
another
Na
e-
Cl
Types of covalent bonds

 Single Covalent bonds- (also called sigma bonds) When a
single pair of electrons is shared
 Ex: H
H
 Group 7A: will form single covalent bonds
 Group 6A: will form two single covalent bonds Ex: H2O
 Group 5A: will form three single covalent bonds Ex: NH3Ammonia
 Group 4A: will form four single covalent bonds Ex: CH4methane
Types of covalent bonds
continued…

 Multiple covalent bonds: Double or Triple bonds
 Double covalent bond- when two pairs of electrons are shared.
 Ex: O2 (draw lewis structure)
 Triple covalent bond- formed when three pairs of electrons are
shared between two atoms. Ex: N2 shares three pairs of
electrons.
 Pi bonds π- multiple bond consists of one sigma and one pi
bond.
 triple bond- one sigma and two pi bonds.
 The shorter the bond the stronger the bond. Triple bonds are shorter.
:
Rules for drawing dot structures:

1. Calculate the number of valence e- each atom
contributes. Divide this number in half to get
the number of pairs.
ex: CBr4
C=4
Br = 7 x 4 = 28
32 e16 prs
3. Use pairs of e- (as single covalent bonds) to
attach all the other atoms to the center atom.
:
ex: CBr4
: Br :
C

: :
: :
: Br
Br :
:
: Br :
4. Put lone pairs of e- on the outside atoms until
each atom has 8 electrons (4 pairs) or 1 pair on
hydrogen.
5. Put any leftover pairs on the center atom so
that it also has 4 prs around it.
Lewis dot structures
continued…

 2. Decide which element will be the center at
usually the one that has fewer atoms or the
lower electronegativity
CH4
SO2
PCl5
Lewis dot structures
continued…

How many
valence
 CH4
electrons does
 What is the central atom?
it have?
4
How many
H
hydrogens are
there?
4
How many
H
H
C
valence
Now, join the electrons with a bond electrons do
each have?
1
H
How many sigma bonds are there?
4
diatomic elements
H2
O2
Br2
F2

I2
N2
Cl2
atoms share electrons in order to
have 8 valence e- (2 for hydrogen)
Naming Covalent Compounds
Covalent compounds are named by adding prefixes to the
element names.

‘Covalent’ means both elements are nonmetals.
A prefix is added to the name of the first element in the formula
ONLY if more than one atom of it is present.
A prefix is ALWAYS added to the name of the second element in
the formula
The second element will use the form of its name ending
in ‘ide’.
Naming Covalent Compounds
Prefixes
Subscript
Prefix
1
mono-
2
di-
3
tri-
4
tetra-
5
penta-

Subscript
Prefix
6
hexa-
7
hepta-
8
octa-
9
nona-
10
deca-
Note: When a prefix ending in ‘o’ or ‘a’ is added to ‘oxide’, the
final vowel in the prefix is dropped.
1
mono
2
di
3
tri
4
tetra
5
penta
6
hexa
7
hepta
8
octa
9
nona
10
deca
* Second element
ends ‘ide’
* Drop –a & -o before
‘oxide’
Naming Binary Covalent
Compounds: Examples
N2S4
 dinitrogen tetrasulfide
NI3
nitrogen triiodide
XeF6
xenon hexafluoride
CCl4
carbon tetrachloride
P2O5
diphosphorus pentoxide
SO3
sulfur trioxide
Writing Chemical Formulas:
A Review

I. Ionic Compounds
II. Covalent Compounds
Writing Formulas for Covalent
Compounds
The names of covalent compounds contain prefixes that indicate the number
of atoms of each element present.

•First element:
• if there is only one atom of that element in the formula (its subscript will
be 1) and there should NOT be a prefix
•Second element:
•will ALWAYS have a prefix
• will ALWAYS end in -ide
Remember:
 Binary compounds contain only two elements, both of which are nonmetals
 When in covalent compounds
atoms DO NOT have charges
Subscripts are determined directly from the prefixes in the
name.
1
Writing Formulas for Binary
Covalent Compounds: Examples
mono
2
di
3
tri
4
tetra
5
penta
6
hexa
7
hepta
8
octa
9
nona
10
deca
* Second element
ends in ‘ide
* Drop –a & -o before
‘oxide’

nitrogen dioxide
NO2
diphosphorus pentoxide
P2O5
xenon tetrafluoride
XeF4
sulfur hexafluoride
SF6
Writing Formulas:
Practice
Analysis
If “Yes”
carbon tetrafluoride
CF4
prefixes  covalent  prefixes indicate subscripts
sodium phosphate
Na3PO4
metal  ionic  balance charges  3 Na1+ needed for 1 PO43-

copper (I) sulfate
Cu2SO4
aluminum sulfide
Al2S3
dinitrogen pentoxide
N 2 O5
ammonium nitrate
NH4NO3
lead (IV) oxide
PbO2
iron (III) carbonate
Fe2(CO3)3
metal present  ionic  balance charges 2 Cu1+ needed for 1 SO42* Are there
prefixes
present
The compound is
covalent: the
prefixes give the
subscripts.
metal present  ionic  balance charges 2 Al3+ needed for 3 S2-
prefixes  covalent  prefixes indicate subscripts
The compound is
ionic:
subscripts
must be
determined by
balancing
charges
polyatomic ion present  ionic  balance charges 
1 NH41+ needed for 1 NO31-
metal present  ionic  balance charges 1 Pb4+ needed for 2 O2-
metal present  ionic  balance charges 2 Fe3+ needed for 3 CO32-