1. COVALENT BONDS OCTET RULE ELECTRONEGATIVITY
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

2. BONDING PATTERNS/REQUIREMENTS pg. 111
Hydrogen (1) Nitrogen (3) Oxygen (2) Halogens (1) carbon (4)
X = F, Cl, Br, I N .. : O .. C H X .. : N +
Nitrogen Ion, N+, (4)

3. BOND GROUP EXCEPTIONS 3 Boron, B Aluminum, Al 4 Silicon, Si 3
Phosphorus, P
also 5 2
Sulfur, S
also 4 & 6 1
Chlorine, Cl
Bromine, Br
also 3 & 5 1
Iodine, I
also 3, 5, & 7

4. 1. Sum the total number of valence electrons from all atoms in subst.
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

5. Draw Lewis structure for phosphorus trichloride, PCl3
1. Total valence e-’s
P: 1s22s2p63s2p3: 5
Cl: 1s22s2p63s2p5: 7 * 3 = 21
total = = 26
2. Central atom: P Attached: 3 Cl’s
3. Place 2 e-’s to
show bonds
Cl:P:Cl Cl ..
= 20 e-’s left to account for .. :
= 0
4. Complete octet :Cl:P:Cl:
: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:

6. P GEOMETRY AB3E Pyramidal :Cl P Cl: :Cl: 3-D DRAWING Cl
4 possible bonding sites, tetrahedral
in this case; 3 bonds, 1 lone pair
GEOMETRY
AB3E Pyramidal ..
:Cl P Cl:
:Cl:
3-D DRAWING P .. Cl :

7. P POLARITY Cl more electronegative than P :Cl P Cl: :Cl:..
:Cl P Cl:
:Cl:
Cl: P: 2.1 ..
:Cl P Cl:
:Cl:
3.0 – 2.1 = 0.9
POLAR BOND
OVERALL POLARITY OF MOLECULE P .. Cl :

8. POLARITY pg. 130 H F H F 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
= 1.9
polar covalent
H F

9. C HCN 10 – 8 = 2 H C N H C N H C N bonds: val. e-: 1 4 3 1 4 5 = 10..
H C N ..
bonds:
val. e-:
= 10 ..
H C N .. .. .. ..
DOT LEWIS D
STRUCTURE STRUCTURE DRAWING
RESONANCE STRUCTURE
moleucle described as blend (composite) of 2+ Lewis structures
CO3-2; carbonate ion
6 – 6 = 0 .. :
12 – 6 = 6 C O .. : ..
C O ..
bonds:
val. e-:
(3) = 22
+ 2e- = 24 .. : :
24 – 6 = 18
18 – 6 = 12

10. .. : C O -2 .. : C O : .. C O

11. GEOMETRY AROUND CENTRAL ATOM Pg. 123
Bonds Lone Pair Geometry Formula Bond
Linear AB
Planar Triangular AB
Angular (Bent) AB2E < 1200
Tetrahedral AB
Pyramidal AB3E
Bent AB2E
Trigonal Bipyramidal AB , 1200
Octahedral AB

12. Condensed: shows atom connections without showing bonds
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 e-
Condensed Structural
Molecular Lewis
C C C C C C OH H
H3C O
(CH3)2CHCH2COCH2CH2COOH
C8H14O3
C C C C C C OH H
H3C O : : : :

13. 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 e-
double bond: 2 pair electrons,
total: 4 e-
triple bond: 3 pair electrons,
total: 6 e-

14. NAMING BINARY COVALENT MOLECULES
1. Use prefixes
1: mono : di : tri : tetra : penta
6: hexa : hepta 8: octa : nona : 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

15. CO2 N2O P2Cl5 N2O4 Carbon Dioxide Dinitrogen Monoxide
Diphosphorus Pentachloride
Dinitrogen Tetroxide
N2O4
Silicon Hexafluoride
SiF6

16. CH4 CHCl3 BF3 CH2Br2 Methane Trichloromethane Boron Trifluoride
Dibromomethane
Diiodine Nonoxide
I2O9

17. ION DIAGRAMS
ClO2-1 or O2Cl-1 (chlorite ion) PO4-3(phosphate ion)
total e-
= = 32
central
Cl P .. .. -1 .. -3
O Cl O .. ..
O P O O

18. RESONANCE
A molecule as a blend of diff structures
as, green, blend primary colors blue & yellow
Ozone, O3 .. .. O .. O .. ..
SO3-2 (sulfite ion) .. O S .. O S .. O S