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Covalent Bond is formed by sharing 1 or more pairs of electrons
H2 = H H nonmetal + nonmetal
8 electrons satisfy an Octect
If the electrons are shared there is no charge-
Ionic Bonds need Balancing-
Covalent Bonds will never conduct electricity-
An ionic solid if soluble in water, forms an aqueous solution that conducts electricity.
A single covalent bond is a covalent bond in which two atoms share one pair of
electrons.
○
A double covalent bond is a covalent bond in which two atoms share two pairs of
electrons.
○
A double covalent bond is approximately twice as strong as a single covalent bond. ○
A triple covalent bond is a covalent bond in which two atoms share three pairs of
electrons.
○
A triple covalent bond is approximately 3 times stronger than a single covalent bond.
The term multiple covalent bond is a designation that applies to both double and triple bond.
○
Slide 5-5
= 5 Valence Electrons
Chapter 5 - Chemical Bonding: The Covalent Bond ModelWednesday, September 26, 20074:31 PM
CHEM 1151 - Organic & Biological Chemistry.one (On 1-6-2008).one (On 6-5-2008) Page 1
When you go from single bond to double bond the length becomes shorter
C2H2 =
carbon always needs 8 electrons, always 4 bonds, no ionic bond
Slide 5-8
Group VIIA and hydrogen cannot form double bonds. Only single bond is possible ○
Oxygen can form either two single bond or one double bond. Other group VIA elements
can form multiple bond Nitrogen can form 3 bond maximum.
○
Carbon always form four covalent bonds. It may be any combination of single, double and
triple bonds.
○
Number of bonding depends upon valence electrons and number of vacancies. ○
We won't see
this Very often
CH4 = C2H4 =
CHEM 1151 - Organic & Biological Chemistry.one (On 1-6-2008).one (On 6-5-2008) Page 2
Group 6 can form single and double bonds
H2O
Slide 5-9
Step 1.
5 + (1 * 3) = 8
group 1 x 3 atoms
Group 5 NH3 Group 1
Step 2. Identify central atom; the central atom is the atom with the least electronegativity
(the first element in a period, the last element in a column)
Step 3.
Example 2 Example 3
Can form one double
and one singe bond
8 - 6 = 2
The number 6 came from
the single bonds. There are two electrons per
bond. So that means we
need Two more electrons.
The two extra electrons go
above nitrogen
Exceptions:Hydrogen can't be the
central atom because it cannot satisfy the
octect rule
-
________________
________________
________________
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Example 2 Example 3
SO2 6 + (6*2) = 18 H2O (1*2) + 6 = 8
Step 1 Step 1
Step 2 Step 2
18-4=14
Step 3
Sulfur needs to have 8
Electrons So we change
the structure to the one
below.
Example 4
Step 1
SO3 6 + (6*3) = 24
Step 1
Example 6
Step 2 CH3OH
24 - 6=18
Example 5
Step 1
H2O2 (2*1) + (6*2) = 14
Step 2
Step 3
Step 3
Step 2
*Note: Fill surrounding atoms first, then
the central atom.
Only double pair when the central atom
needs to fill the octect. Ex. C2H4.
Carbon can form a maximum of 4 bonds.
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# of lone pair
electrons on 'central'
atom
# of bonding
groups (pair electrons) on
'central' atom
Electron-pair
Geometry
Molecular Geometry
BondAngl
e
0 2 linear linear 180
0 3 trigonal
planar
trigonal planar 120
1 2 trigonal
planar
bent less
than 120
0 4 tetrahedral tetrahedral 109.
5
1 3 tetrahedral trigonal
pyramidal
less
than 109.
5
2 2 tetrahedral bent less
than 109.
5
0 5 trigonal
bipyramidal
trigonal
bipyramidal
90,
120 and
180
1 4 trigonal
bipyramidal
seesaw 90,
120 and
180
2 3 trigonal
bipyramidal
T-shaped 90
and
CHEM 1151 - Organic & Biological Chemistry.one (On 1-6-2008).one (On 6-5-2008) Page 5
bipyramidal and 180
3 2 trigonal
bipyramidal
linear 180
0 6 octahedral octrahedral 90
and 180
1 5 octahedral square pyramidal 90
and 180
2 4 octahedral square planar 90
and 180
Pasted from <http://intro.chem.okstate.edu/1314F00/Lecture/Chapter10/VSEPR.html>
Prefi
x
Num
ber
Mono
-
1
Di- 2
Tri- 3
Tetra
-
4
Penta
-
5
Hexa- 6
Hepta
-
7
Octa- 8
Nona
-
9
Deca- 10
Linear Bent or Angular
Examples: Naming Molecular Compounds (PG 119)
N2O3 Dinitrog
en Trioxide
P4O10 Tetraph
osphate Decaoxi
de
NCl3 Nitrogen
Trichloride
NCl5 Nitrogen
Pentachloride
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Trigonal planar
Tetrahedral
Trigonal bipyramidal
Octahedral
Bent or Angular
Sawhorse or Seesaw
T-shape
Linear
Square pyramidal
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Pentagonal bipyramidal
Bent or Angular
Trigonal pyramidal
Square planar
T-shape
Linear
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Geometry of Molecules
Areas ofElectron
Density
Electro
n Pair Geome
try
Bondi
ngareas
Lone Pairs
Molecular
geometry
Angle
s
2 Linear 2 0 Linear 180°
3 Trigona
l planer
3 0 Trigonal
planer
120u
3 Trigona
l planer
2 1 Bent /
Angular
120°
4 Tetrah
edral
4 0 Tetrahedral 109.5
°
4 Tetrah
edral
3 1 Trigonal
pyramidal
109.5
°
4 Tetrah
edral
2 2 Bent /
Angular
109.5
°
Lewis Structure of Ionic Compound
Only draw the structure for the covalent bond
Example:
K2SO4
K + SO42-
[K]+ [K]+
2-
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If the central atom has a loan pair the molecular geometric shape will be different than the ○
electronic geometry. If the central atom has no loan pair, then the electronic and molecular
geometries are the same.
Periods 1 & 2 = 2 ns2np6○
Periods 3 and up can have more than eight electrons on the central atoms (D orbital) in some
cases.
○
Electronegativity is the relative tendency of a bonded atom to attract electrons to itself.○
An atom with extremely low electronegativity, like a Group I metal, is said to be electropositive ○
since its tendency is to lose rather than to gain, or attract, electrons
Electronegativity decreases down a Group in the Periodic Table as the atomic radius and number of ○
inner electron shells both increase. Electronegativity increases across a Period of the Periodic Table, in general, due to increasing
nuclear
○
charge and decreasing atomic radius. The electronegativity Scale was developed by Pauling○
F is the higher electronegativity element with the value of 4○
Each Lone Pair counts as one electron domain.•
Each Single Bond counts as one electron domain.•
Each Double Bond counts as one electron domain.•
Each Triple Bond counts as one electron domain.•
Polarity of Covalent Bond
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The polarity in the bond can also be represented by
a arrow indicating a dipole (two charges separated by a distance). The tip of the arrow points toward
the more electronegative atom.
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