1. VSEPR FLOWCHART
How many things are stuck to the atom? “Things” refer to other atoms or lone pairs, NOT bonds (single or double or triple).
ONE
H2, only example
Linear, F2
TWO
THREE
FOUR
How Many Lone Pairs on the Atom?
How Many Lone Pairs on the Atom?
How Many Lone Pairs on the Atom? 3 2
Linear, O2 1 2 1
Tetrahedral, CH4
Bent,
H2O 1
Linear, CO2
Linear, N2
Trigonal Planar, BCl3
Bent, O3
Trigonal Pyramid, NH3

2. VSEPR FLOWCHART
How many things are stuck to the atom? “Things” refer to other atoms or lone pairs, NOT bonds (single or double or triple).
FIVE
How Many Lone Pair on the Atom?
Linear, IF2
Trigonal Bipyramid, PF5
Seesaw, SF4
Linear, ?
T-shaped, ClF3

3. VSEPR FLOWCHART
How many things are stuck to the atom? “Things” refer to other atoms or lone pairs, NOT bonds (single or double or triple).
SIX
How Many Lone Pair on the Atom?
Square Pyramid, BrF5
Octahedron, SF6
Square Planar, XeF4

4. Polarity and Dipole Moments
Basic Concept: The electrons of most chemical bonds are unequally shared. The reason for this inequality is that the atoms forming a bond have different abilities to attract electrons
Electronegativity is a measure of the relative attraction that an atom has for the shared electrons in a bond.
The bond polarity (bond dipole moment) is a measure of the inequality in the sharing of bonding electrons.

5. The separation of positive and negative charges causes an electric dipole moment and this dipole moment is a vector…
Vectors have a magnitude and a direction. You add vectors by adding their projections on the x, y, and z axes.
The dipole moment points from the atom with the smaller electronegativity to the atom with a larger one.
NaCl looks like Na+Cl- in the gas phase and the dipole points from Na to Cl.
If the vector sum of bond polarities (bond dipole moments) of a molecule is not zero, the molecule is said to be polar and to have a dipole moment.

6. Polarity of Molecules
A molecule is polar if there exists a NET charge separation between two “ends” of the molecule (i.e., a negative ‘end’ and a
positive ‘end’).
To have a net dipole:
1. polar bonds;
2. Geometry where bond dipoles do not cancel.

7. Discussion Topics on Dipole Moments
Is there a dipole moment for CO CS
CO2
CS2
OCS O2 O3 S2
SO2

8. Examples of Dipole Moments
Discuss dipole moments and polarity of
CH4
CH3Cl
CH2Cl2
CHCl3
CCl4
Use the VSEPR model to predict the shapes of these compounds. Which compound is expected to be most polar and which is nonpolar?
Discuss what would be the result if the structure of these compounds were square planar.

9. Chemical Processes in Solutions
Dissolution (two or more substances spread
out into each other at the level of individual atoms/molecules/ions)
solution

10. Solutions Solvent (e.g, H2O) Solute solution C12H22O11(s) C12H22O11(l)
Only solvent-solvent interactions
Solute
solution
Only solute-solute interactions
C12H22O11(s) C12H22O11(l)
Some solvent-solute interactions

11. Molarity of a Solution 5.84 g 5.84 g 100 ml H2O 5.84 g NaCl=
M(NaCl)
58.4 g/mol
= mol
5.84 g NaCl in x(≠100) ml
Solution changes density
as NaCl is added to pure H2O

12. How to make a 1 Molar Solution
Instead, dissolve 5.84 g NaCl in less than 100 ml of H2O; then fill up solution to 100 ml.
n =
5.84 g
M(NaCl)
58.4 g/mol =
mol
If you fill up to 100 ml, you are sure that you have
5.84 g NaCl
100 mL
mol =
0.100 L
mol L
1.00
= 1.00 M

13. Practice Problem on Molarity
What is the molarity of a 400 mL solution of 20 g of MgCl2?
m(MgCl2) = 20 g
M(MgCl2) = ( x ) g/mol = g/mol
m(MgCl2)
M(MgCl2)
n(MgCl2) =
20 g
g/mol
= 0.21 mol
0.21 mol
400 ml
0.400 l
= 0.52 M

14. Ionic Compounds in Water
Many ionic compounds (although not all of them -- see below) dissolve readily in water. The ionic bond is strong. How are the solute-solute forces overcome by dissolving the ionic solid in water?
+ H2O
NaCl(s)
Na+(aq)
aquation +
Cl-(aq)
H2O:
dissociation

15. Molecular Substances in Water
Definition of Solubility: The solubility of a substance is the largest amount that can dissolve in a given amount of a solvent at a particular temperature.
If solute molecules are sufficiently polar, strong interactions between the solute molecules and the water molecules lead to good solubility characteristics of the system (sugar and water mix very well).
Some compounds however are not sufficiently polar to interact strongly enough with water and hence they show very poor solubility in water (think of your salad dressing! -- oil and water barely mix)
General rule for solubility is : LIKE dissolves LIKE!

16. Electrolytes, Weak and Strong
Electrolytes are compounds that ionize in water to produce aqueous solutions that conduct an electric current.
Nonelectrolytes are substances that do not ionize, remain as molecules, and do not conduct an electric current.
Strong electrolytes are molecules that ionize 100% (or nearly so) and conduct an electric current well.
Weak electrolytes barely or partially ionize; most molecules remaining un-ionized, and conduct an electric current poorly.

17. Examples Nitric acid (HNO3) is a strong electrolyte.
HNO3  H+1 + NO3-1
If 1.00 mole of HNO3 is dissolved in water, it will ionize to produce 1.00 mole of H+1 and 1.00 mole of NO3-1 . There will not be any HNO3 left, unionized.
By contrast, one mole of a weak electrolyte will produce much less than 1.00 mole of its constituent ions. One mole of acetic acid
HC2H3O2 ↔ H+1 + C2H3O2-1
might produce 0.05 moles of H+1 and 0.05 moles of C2H3O2-1 and still contain 0.95 moles of the original acetic acid.

18. Another Example:
Calculate the concentrations of ions in a M Ba(OH)2 solution. Ba(OH)2 is a strong electrolyte.
Hint: What is the valency of Ba? What ion will it form? Where will the extra electrons go?