1. Covalent Bonding
The joining of two or more elements through the sharing of valance electrons to form a molecule
Purpose: To form a stable octet between the elements

2. Types of Covalent Bonds
Non-Polar: equal sharing of the valance electrons.
Polar: unequal sharing of the valance electrons.

3. Non-Polar Shape of molecule is symmetrical. Homonuclear molecules.
Diatomic molecules:
N2, O2, F2, Cl2, Br2, I2, and H2
Makes the #7

4. Polar
Shape of the molecules is asymmetrical due to unequal sharing of the electrons.
Heteronuclear: one nuclear charge is stronger than another.
Polarity is the function of the change in electronegativity (DEN)
Increase DEN, = more ionic chstc.

5. Polar Molecules Rank these in decreasing covalent characteristics:
H2O, N2, NO3- , NaBr2, CO2
Solution:
1. Identify the electronegativity for each element in the molecule.
2. Less covalent > 1.7 > more covalent.
N2 > NO3- > CO2 > H2O > NaBr2

6. Lewis Dot Structure Pictorial representation of valance electrons.
Stick structure

7. Octet Rule
Representative elements share electrons to take on a Noble gas electron configuration.
Each element in a molecule will follow the octet rule.

8. Shared Electrons Formula to determine the number of shared electrons:
N – A = S
N = # of electrons needed to form a Noble gas configuration.
A = # of electrons available in the valance.
S = # of electrons shared

9. Bonding Sigma Bonds are the single electron overlap of the s orbital.
Forms single bonds, end-to-end.
Pi Bonds are the overlap of the s and p orbitals.
Forms double and triple bonds w/ s end-to-end and p side-to-side.

10. Practice Problems CO2 N2 CS2 HNO3 NO31- Which are polar?
Which are non-polar?
Which are non-polar with polar bonds?

11. Resonance
Equally acceptable formulas.
HNO3
NO31-

12. Limits to the Octet Rule
Most beryllium compounds
Most Group IIIA elements
Compound which require more than 8e- in the valance.
Compounds containing d or f transitional elements
‘S’ with an odd number of electrons

13. Practice Problems
CCl4
CO2
N2O5
N2O
S3O5
NF3

14. Naming Molecules
Follows the rules as ionic compounds except prefixes are used to note ‘how many’.
Table 8-3, page 248.

15. Molecular Structure VB Theory : Valance Bond Theory, orbital overlaps
VSEPR Theory: Valance Shell Electron Pair Repulsion Theory
Electrons arrange to max the distance between electrons
Bonding pairs v. Unshared pairs

16. Molecular Geometry Linear (2) Trigonal Planar Tetrahedral
Trigonal Pyramidal
Angular (Bent)
Trigonal Bipyramidal
Octehedral

17. Linear Formula AB2 w/ no unshared pairs VSEPR: bonding angle of 180o
VB: sp overlap
Forms a polar bond and a non-polar molecule.

18. Trigonal Planar Formula of AB3 and no unshared pairs.
VSEPR: bonding angle of 120o
VB: SP2 overlap
Polar bond w/ non-polar molecule

19. Tetrahedral Formula of AB4 w/ no unshared pairs.
VSEPR: bonding angle of 109.5o
VB: sp3 overlap
Forms polar bonds and non-polar molecule.

20. Trigonal Pyramidal Formula AB3 w/ one unshared pair on A.
General: subtract 2.5o for each unshared pair.
VSEPR: bonding angle of 107o
VB: sp3 overlap w/ a polar bond and a polar molecule

21. Angular (Bent) Formula AB2 w/ 2 unshared pairs on A
VSEPR: bonding angle of 104.5o
VB: sp3 overlap w/ polar bonds and polar molecule.

22. Linear Formula AB w/ 3 unshared pairs VSEPR: bonding angle of 102o
VB: sp3 overlap w/ polar bonds and polar molecule.

23. Trigonal Bipyramidal Formula AB5 w/ no unshared pairs
VSEPR: bonding angles at 90o, 120o and 180o
VB: sp3d overlap w/ polar bonds and polar molecule.

24. Octahedral Formula AB6 w/ no unshared pairs
VSEPR: bonding angles of 90o, 120o and 180o
VB: sp3d2 overlap w/ polar bonds and molecule

25. Molecules
Molecule VB VSEPR Shape
NI3
PH3
CH4
SF6
H2S
PF5
BeCl2