1. Naming Binary Covalent Compounds
The first element in the formula is named first, followed by the second with the suffix -ide
Prefixes are added to the elements name for both the first and the second
mono- 1
di- 2
tri- 3
tetra- 4
penta- 5
hexa- 6
hepta- 7
octa- 8
nona- 9
deca- 10
Never use mono- for the first element

2. Polar and Non-polar Covalent Bonds
Reminder: The ability of an atom within a molecule to draw electrons toward itself is called electronegativity.
An electron pair shared between two atoms of the same element is called a non-polar covalent bond
N2, H2, F2 all have non-polar covalent bonds
Each element has the same electronegativity so both atoms attract electrons equally.

3. Polar and Non-polar Covalent Bonds
What if two different atoms with different electronegativities? HF
H = 2.2, F = 4.0 so F will attract electron better
An electron pair is more likely to reside closer to the nucleus of the atom with the greater electronegativity and forms a polar covalent bond. The greater the difference between the electronegativites, the more polar the bond.
H F

4. Polar and Nonpolar Covalent Bonds
What if the difference between the electronegativities is really large?
Na and F
Na = 0.93, F = Difference is 3.07!
Called an ionic bond.

5. Polarity of Molecules
Just as bonds can be polar (electronegativity of atoms) so can molecules
If the atoms attract electrons around the central atom symmetrically, the molecule is non-polar C O B F O H
If the atoms pull electrons around the central atom asymmetrically, the molecule is polar

6. Oil and Water Oil is non-polar Water is polar
That is why oil and water don’t mix

7. VSEPR Theory Valence Shell Electron Pair Repulsion Theory
Use VSEPR to predict the shape of molecules based on the Lewis structure
Shape of the molecule is affected by each of the valence shell electron pairs surrounding a central atom
The regions of electron space around the atom repel each other and strive to get as far away from each other a possible
Region of electron space are:
a non-bonding lone pair
bonding electrons

8. Possible VSEPR Shapes
5 VSEPR shapes corresponding to number of regions of electron space
6 regions: Octahedron
5 regions: Trigonal bipyramid
4 regions: Tetrahedron ° apart
3 regions: Trigonal Planar ° apart
2 regions: Linear ° apart

9. Predicting Shape - CH4 C H 1. Draw Lewis Structure of Molecule
2. Count regions of electron space around central atom
- Each bonding region (single, double or triple bond) counts as one
- Each lone pair counts as one
3. Assign VSEPR shape
4 Regions
4. Place lone pairs (if applicable) on shape
Tetrahedron
No Lone Pairs
5. Assign structure by positions of the bonded atoms
Tetrahedron

10. Predicting Shape - H2O O H 1. Draw Lewis Structure of Molecule
2. Count regions of electron space around central atom
- Each bonding region (single, double or triple bond) counts as one
- Each lone pair counts as one • O H
3. Assign VSEPR shape
4 Regions
4. Place lone pairs (if applicable) on shape
Tetrahedron
2 Lone Pairs
5. Assign structure by positions of the bonded atoms
Bent

11. Shapes of Molecules

12. Group Work
Predict the shape and polarity (polar or non-polar) of the following molecules
NH3
BCl3 HF

13. Interactions between molecules
Three phases of matter
Solid
ordered structure
fixed volume and shape independent of container
Strong interaction between molecules
Liquid
loosely ordered
fixed volume, but not fixed shape - dependent on container
Moderate interaction between molecules
Gas
No order
Volume dependent on container
Always occupies all of its container
Almost no interaction between molecules