1. Covalent Bonding

2. Covalent Bonding Covalent bond –formed from the sharing of electrons
Usually between 2 non metallic elements

3. Molecules Molecule – two or more atoms covalently bound together
Diatomic molecule – two of the same atom bound together

4. Diatomic Molecules Br I N Cl H O F or the Magnificent 7
These atoms never exist alone.
They always come in pairs
For example:
Br  Br2
I  I2
N  N2
Cl  Cl2
H  H2
O  O2
F  F2

5. Binary Molecular Compounds
Binary Compounds consist of 2 elements
Binary covalent compounds can be recognized by containing 2 nonmetals
This is different from ionic compounds that contain a metal & nonmetal, metal & a polyatomic ion, or 2 polyatomic ions

6. Lewis Structure
Lewis Structures – shows how the valence electrons are arranged among the atoms of a molecule
There are rules for Lewis Structures that are based on the formation of a stable compound
Atoms want to achieve a noble gas configuration

7. Octet & Duet Rules Octet Rule – atoms want to have 8 valence electrons
Duet Rule – H is the exception. It wants to be like He & is stable with only 2 valence electrons

8. Steps for drawing Lewis Structures
Sketch a simple structure with a central atom and all attached atoms
Add up all of the valence electrons for each individual atom
If you are drawing a Lewis structure for a negative ion add that many electrons to create the charge
If you are drawing a Lewis structure for a positive ion subtract that many electrons to create the charge

9. Steps for drawing Lewis Structures
Subtract 2 electrons for each bond drawn
Complete the octet on the central atom & subtract those electrons
Complete the octet on the surrounding atoms & subtract those electrons
Get your final number
If 0  you are done!
If +  add that many electrons to the central atom
If -  need to form multiple bonds to take away that many electrons

10. Examples
CCl4
Sketch a simple structure with a central atom and all attached atoms Cl │
Cl – C – Cl

11. Examples Add up all of the valence electrons for each individual atom
4 + 4(7) = 32
Subtract 2 electrons for each bond drawn
32-8 = 24
Complete the octet on the central atom & subtract those electrons
Done

12. Examples
Complete the octet on the surrounding atoms & subtract those electrons
24 – 24 = 0
Final number = 0…DONE!
Final structure is… __
│Cl │
__ │ __
│Cl – C – Cl │ │

13. Examples N2

14. Examples
NH3

15. Examples
PO4 -3

16. Bond Types Sigma bonds () – single covalent bond
Pi bonds () – occur when multiple bonds are formed
Single bond – sigma
Double bond – 1 sigma & 1 pi
Triple bond – 1 sigma & 2 pi

17. Bond length & Strength
As the number of bonds increases, the bond length decreases
The shorter the bond, the stronger the bond