1. Drawing Molecules and Shapes

2. Lewis Structures Structural formula Valence electrons are dots
How to draw:
Write the symbol of the element
Place one dot on each side of the symbol until all e- are represented
Used to show bonding
Dot pairs or dashes between two atomic symbols represent covalent bonds.

3. Single Elements Al Br Ne C

4. Two chlorine atoms covalently bond
Each atom contributes one electron to a shared pair
An unshared pair, or a lone pair, is a nonbonding pair of electrons

5. Multiple bonds are stronger and have shorter bond length
The number of bonds shared between two atoms determines the kind of bond
Single
Double
Triple
Multiple bonds are stronger and have shorter bond length

6. Draw a Lewis Structure for HCl

7. Draw a Lewis structure for CH3I.

8. Draw a Lewis structure for the sulfate ion, SO4-2
Remember the -2 means that overall 2 electrons are added
They can be added where needed

9. For O2 to make an octet, each atom needs two more electrons
For O2 to make an octet, each atom needs two more electrons. The two atoms share four electrons.

10. Molecular geometry

11. VSEPR Valence Shell Electron Pair Repulsion Theory
Predicts molecular shapes
pairs of valence electrons surrounding an atom repel each other to create shape
Shape determined electrons surrounding the central atom.
Shared pairs that form different bonds repel each other and remain as far apart as possible.
See chart for determining the shape of a molecule.

12. BI3
Trigonal planar
SCl2
bent

13. polarity

14. Polarity Shape effects polarity
Polarity of a molecule depends on the polarity of each bond and the way bonds are arranged
2 dipoles in opposite directions cancel each other out = nonpolar
2 dipoles at an angle don’t cancel = polar

16. AsF3

17. CH4