7. 4f 5f

10. Ionization Energy Trends

11. Electronegativity Increasing Electronegativity
Decreasing Electronegativity

13. Lewis Structure Assumptions
Only valance electrons are involved in bonding.
Atoms react to form molecules, so to achieve stable noble gas electron configurations.
Atoms in molecules want eight valance electrons (octet rule) except for hydrogen which wants two electrons (duet rule).
In covalent compounds atoms share electrons to form bonds in order to achieve stable noble gas electron configurations. In ionic compounds electrons are transferred from one atom to another to achieve stable noble gas electron configurations.

14. Rules for Drawing Lewis Structures
Step 1: Count the total number of valance electrons.
Step 2: Identify the central atom (the first atom written unless that atom
is hydrogen). Place all terminal atoms around that atom.
Hydrogen atoms NEVER have more than one bond.
Step 3: Complete the octet for all atoms in the Lewis structure with
lone pairs of electrons (except hydrogen).
Step 4: Check your structure by counting the number of valance
electrons used (they will match step 1 if the structure is
correct). If your valance electrons don’t match you will need
to tweak your structure as follows.

15. Tweaking Lewis Structures
Too Many Electrons Initially: Redraw the
Lewis structure from step 2 adding a double
bond. If you still have too many electrons
add another multiple bond and repeat.
Always add double bonds before triple
bonds. Every double bonds effectively
remove two electrons from the structure while
triple bonds effectively remove 4 electrons.

16. “Exceptions” to the Octect
Two Few Electrons: If you only have four or
six valance electrons initially you can’t
possibly fill the octet rule (usually BeH2 or
BH3). Just place hydrogens around central
atoms and call it done.

17. “Exceptions” to the Octect
Odd number of electrons: One atom will
have to have less than eight electrons.
Draw the Lewis structure as if it had one
more valance electrons than it actually does.
Then subtract one electron from the least
electronegative element (often the central
atom).

18. “Exceptions” to the Octect
Exceeding the Octet Rule: If the central atom is in
the third row or below it may be possible to exceed
eight electrons around the central atom. But only if
you absolutely have no choice. If you can give
everything eight and only eight do that first. When
you must break the octet rule draw the structure as
you would in steps 1-4 and the place the extra
electrons around the central atom. Even when
breaking the octet rule no atom will ever have
more than 12 electrons.

19. CO2 2 180 sp CH2S 3 120 sp2 SeO2 1 SiCl4 4 109.5 sp3 PCl3 H2S HI
Example
Total # of Things
Lone Pairs
Geo.
Shape
3-D Lewis
Structure
Bond Angles
Hybrid Orbitals
CO2 2
Linear
180 sp
CH2S 3
Trig.Planar
Trig. Planar
120
sp2
SeO2 1
Bent
SiCl4 4
Tetra.
109.5
sp3
PCl3
Trig. Pyramid.
H2S HI

20. PF5 5 SeBr4 1 BrCl3 2 XeCl2 3 TeF6 6 IF5 RnBr4 dsp3 d2sp3 120, 90, 180
Example
Total # of Things
Lone Pairs
Geo.
Shape
3-D Lewis
Structure
Bond Angles
Hybrid Orbitals
PF5 5
Trig. bipyramid
120, 90, 180
dsp3
SeBr4 1
See-saw
BrCl3 2
T-shaped
90, 180
XeCl2 3
linear
180
TeF6 6
Octahed.
d2sp3
IF5
Square pyramid
RnBr4
Square planar

21. Organic Lewis Structure Rules
Based on formal charge arguments
Atom
Bonds Formed in Lewis Structure
Lone Pairs on Atom in Lewis Structure C 4 N 3 1 O 2
F, Cl, Br, I

22. p-orbitals are 90 degrees from each other

23. 1 s + 3 p = 4 sp3 orbitals

24. 1 s + 2 p = 3 sp2 orbitals

25. 1 s + 1 p = 2 sp orbitals

26. Unhybridized p-orbitals delocalize the -electrons

27. ALL atoms are sp2 hybridized in NO31-
ALL atoms are sp2 hybridized in NO31-. There are NO sp3 hybridized orbitals.