1. Predicting Shapes of Molecules
VSEPR
Valence Shell Electron Pair Repulsion Theory

2. Why not the shape of ionics?

3. Linear (straight line)
Any 2 atom molecule is linear O2 H2
HCl etc.

4. Steps to predicting shapes
Draw the dot structure
Count the electron domains surrounding the central atom
Single bonds count as one
Double and triple bonds count as one
lone electron pairs (unbonded) count as one

5. Determine the category (electron geometry) based on regions of electron domains
2 domains - Linear
3 domains – trigonal planar
4 domains - tetrahedral
5 domains – trigonal bipyramidal
6 domains - octahedral

6. FINALLY
Name the shape of the molecule (molecular geometry)
based on the arrangement of the ATOMS
Lone pairs are repulsive and force the bonded electrons together and reduce the bond angles AND change the shape

7. Practice… Shape & bond angles?
H2Se
Bent w/ ~1050 angles
CH2Cl2
Tetrahedral w/ 109.5o angles
PCl3
Trigonal pyramidal w/ 107o angles

8. Types of Covalent MOLECULES POLAR vs. NON-POLAR

9. non-polar
Have symmetrical electron distributions. IF THERE ARE POLAR bonds, they all cancel each other out.

10. Polar molecules (a.k.a. Dipoles)
Occurs because of a polar bond between 2 atoms O C δ- δ+

11. Or uneven charge (e-) distribution in the moleculeCl H δ- δ+

12. Another example of asymmetrical distribution of electrons
Trigonal pyramidal Bent
polarity

13. Water is asymmetrical δ- O H H δ+

14. Water is a bent moleculeH H

15. W - A - T - E - R as bent as it can be! Water’s polar MOLECULE!
The H is positive
The O is not - not - not - not

16. W - A - T - E - R as bent as it can be! Water’s polar MOLECULE!
The H‘s are the ears
The O’s the nose - nose - nose - nose

17. W - A - T - E - R
as bent as it can be!

18. Making sense of the polar non-polar thing
COVALENT
BONDS or MOLECULES
non-polar are between identical atoms or very small e-neg difference up to ~0.4
All other bonds with e-neg difference up to ~2.0 are polar
Non-polar
Even distribution of electrons
Polar bonds cancel out cancel
Polar
asymmetrical UNEVEN electron distribution

19. The End