COVALENT BONDS
1. Bonds formed by sharing electrons between atoms
2. Group of atoms held together by covalent bond, called molecule
OCTET RULE
1. 8 electrons (4 pair) around atom -- Hydrogen 2 e-’s or 1 pair
2. Occurs mostly with Main Group Elements (IA-VIIIA)
3. Results in Noble Gas electron configuration for each atom
ELECTRONEGATIVITY
The ability of an atom to attract pair of electrons in covalent bond
F, fluorine, most electronegative element
P.table: most upper right of table
least lower left of table
use  to show partial “+” charge on less electroneg. atom

use  to show partial “-” charge on more electroneg. atom

BONDING PATTERNS/REQUIREMENTS
pg. 111
Hydrogen (1)
Nitrogen (3)
Oxygen (2)
Halogens (1)
X = F, Cl, Br, I
carbon (4)
..
N
H
O
..
X
..
:
C
..
N
:
O
C
N
C
+
Nitrogen Ion, N+, (4)
N
C
BOND GROUP EXCEPTIONS
3
Boron, B
Aluminum, Al
2
Sulfur, S
also 4 & 6
4
Silicon, Si
1
Chlorine, Cl
Bromine, Br
also 3 & 5
3
Phosphorus, P
also 5
1
Iodine, I
also 3, 5, & 7
LEWIS STRUCTURES
pg. 122
Helps in understanding bonding in cmpds/molecules
STEPS
1. Sum the total number of valence electrons from all
atoms in subst.
2. Identify central atom. Write chem.symbols of atoms to show
which atoms are attached to each other
3. Place 2 e-’s to show a bond between each atom
4. Complete the octet rule for each atom
5. If not enough e-’s to give central atom octet, try multiple bonds
Draw Lewis structure for phosphorus trichloride, PCl3
1. Total valence e-’s
P: 1s22s2p63s2p3: 5 Cl: 1s22s2p63s2p5: 7 * 3 = 21
2. Central atom: P
Attached: 3 Cl’s
3. Place 2 e-’s to
show bonds
Cl:..P:Cl
Cl
4. Complete octet
total = 5 + 21 = 26
26 - 6 = 20 e-’s left to account for
.. .. ..
:Cl
.. :P
.. :
.. :Cl
20 - 20 = 0
:
:Cl
..
5. No e-’s left, no multiple bonds
Final step, replace bonding pairs with line
to represent the bond(s) between
..
:Cl
..
..
..
P Cl
.. :
:Cl:
..
GEOMETRY
4 possible bonding sites, tetrahedral
in this case; 3 bonds, 1 lone pair
AB3E Pyramidal
..
..
:Cl
..
..
P Cl
.. :
:Cl:
..
3-D DRAWING
..
..
: Cl
..
P
..
:Cl
..
..
Cl
.. :
POLARITY    
Cl more electronegative than P


Cl: 3.0
..
..
..
:Cl..

P: 2.1
P ..Cl:

:Cl:
..


..
:Cl..
3.0 – 2.1 = 0.9
POLAR BOND
..
P ..Cl:
:Cl:
..
OVERALL POLARITY OF MOLECULE
..
..
: Cl
..
P
..
:Cl
..
..
Cl
.. :
..
POLARITY
pg. 130
Nonpolar: equal sharing of e- pair in bond
occurs when electronegativity value is less than 0.5
all diatomics are nonpolar
Polar: unequal sharing e- pair in bond
occurs when electronegativity diff. between 0.5 & 2.0
Determine electronegativity value, show δ partial charges,
and overall polarity in the molecule, HF
H
F
2.1 4.0
4.0 - 2.1 = 1.9
polar covalent

-
H
F
HCN
H C

H C N
DOT
STRUCTURE
N


RESONANCE STRUCTURE
moleucle described as blend (composite) of 2+ Lewis structures
6–6=0
12 – 6 = 6
:O
..
O
2
6 (3) = 22
+ 2e- = 24
..
C
bonds: 4
val. e-: 4
..
24 – 6 = 18
N
-
LEWIS
STRUCTURE
CO3-2; carbonate ion
H C
..
....
..
-
..
N
3
5 = 10

..
C
4
4
..
H
bonds: 1
val. e-: 1
10 – 8 = 2
O
C
O
18 – 6 = 12
3-D
DRAWING
..
-2
..
:O
C
C
O
O
..
O:
-2
:O
O
..
O
-2
O
C
O
GEOMETRY AROUND CENTRAL ATOM
Pg. 123
Bonds
Lone Pair
Geometry
Formula
2
0
Linear
AB2
1800
3
2
0
1
AB3
AB2E
1200
< 1200
4
3
2
0
1
2
5
0
6
0
Planar Triangular
Angular (Bent)
Tetrahedral
Pyramidal
Bent
AB4
AB3E
AB2E2
Trigonal Bipyramidal AB5
Octahedral
AB6
Bond
109.50
1070
1050
900, 1200
900
FORMULA TYPES
Condensed: shows atom connections without showing bonds
Molecular: shows how many of each diff. atom in molecule
Structural: shows lines (bonds) between atoms to show connection of atoms
Lewis: shows bonds & lone pair eCondensed
(CH3)2CHCH2COCH2CH2COOH
Molecular
C8H14O3
Structural
H H O H H O
H3C C C C C C C OH
H3C
H
H H
Lewis
H H O H H O
H3C C C C C C C OH
H3C
H
H H
VSEPR
Valence Shell Electron-Pair Repulsion
1. Method to predict molecular shape based upon electron charge around atoms
2. Assume electron cloud regions will repel and orient as far apart as possible
from each other
3. States, “bonding electrons & lone electron pairs of an atom will adopt
a spatial arrangement that minimizes electron-pair repulsion around that atom”
MULTIPLE BONDS (between atoms)
Single bond: 1pair electrons,
total: 2 edouble bond: 2 pair electrons,
total: 4 etriple bond: 3 pair electrons,
total: 6 e-
NAMING BINARY COVALENT MOLECULES
1. Use prefixes
1: mono
2: di
3: tri
4: tetra
5: penta
6: hexa
7: hepta
8: octa
9: nona
10: deca
2. 1st element: name of element, no prefix unless more than 1 for subscript
3. 2nd element: name, ending changed to-ide, always use prefix
CO
2nd: oxygen, -ide ending
only 1, prefix mono
1st: carbon; only 1, no prefix
Carbon Monoxide
CO2
Carbon Dioxide
N2O
Dinitrogen Monoxide
P2Cl5
Diphosphorus Pentachloride
Dinitrogen Tetroxide
N2O4
Silicon Hexafluoride
SiF6
CH4
Methane
CHCl3 Trichloromethane
BF3
Boron Trifluoride
Dibromomethane
Diiodine Nonoxide
CH2Br2
I2 O 9
5 + 24 + 3 = 32
P
..
..
....
-1
O
-3
..
..O .. P .. ..O
..
..
..
..
...... ....
..O Cl ..O
..
central
7 + 12 + 1 = 20
Cl
..
total e-
PO4-3(phosphate ion)
....
..
ClO2-1 or O2Cl-1 (chlorite ion)
DIAGRAMS
O
..
ION
RESONANCE
A molecule as a blend of diff structures
as, green, blend primary colors blue & yellow
..O
O
Ozone, O3
..
O
O
O
O
S
O
..
..
O
O
S
S
O
O
..
O
..
..
..
SO3-2 (sulfite ion)
O
O
O