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. Covalent bonds when atoms share e-
Usually each atom contributes one e- to the shared pair
Lone pairs are pairs of e- that are not shared
In some situations one atom can share a whole pair of e-

5. Atoms can share one or more pairs of e-
Each pair that is shared creates a bond
There can be single, double, or triple bonds
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 NF3

9. Draw a Lewis structure for O2
each atom needs two more electrons, so the two atoms share a total of four electrons.

10. Draw a Lewis structure for OH-
Remember the (–) means the ion has gained that many e-

11. Molecular geometry

12. 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 by electrons surrounding the central atom.
Bonded pairs repel each other and remain as far apart as possible.
Lone pairs take up space and must be considered as well
See chart for determining the shape of a molecule.

14. BI3
Trigonal planar
SCl2
bent

15. polarity

16. 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

18. AsF3

19. CH4