11/24
I’m home with my baby today
because my mother-in-law had to go home ;)
But we are still learning!
Sit in your assigned seat, 5th period!
Over Thanksgiving Break
• No homework
• Spend time with the people you love
Plan for today
• Go over homework answers
• Get a reminder on polar bonds and polar molecules
• Complete a station ‘activity’
Homework answers – show your lewis
structure to the sub to get homework
credit
Update your chart with the angles
shown in green
DO NOT TAKE NOTES
• These slides are posted on the website
• Just listen and try to understand
• Ask questions
• I mean, you can write down a bit if you really want to. I don’t think you need to, though….
What makes a molecule polar?
• That depends on the polarity of the bonds in the
molecule AND the arrangement of those bonds
(shape of the molecule)
Nonpolar Covalent Bonds
• Covalent bonding involves sharing electrons between
atoms.
• Nonpolar covalent bond – equal sharing of electrons
between two atoms.
• Both atoms have same attraction for shared pair (they
have the same electronegativity or very close).
• Example: H – H
Polar Covalent Bonds
• Polar covalent bond – unequal sharing of electrons
between atoms.
• One atom has greater attraction for shared pair. (Think:
Tug – of – War).
• Example: H – Cl
• This creates partial (d) charges on each atom in the bond.
The atom with the higher electronegativity has the partial
negative charge.
• We have been talking about whether or not the
bonds were polar
• Now lets talk about whether or not the molecule is
a polar as a result of the polar bonds
Molecular Polarity
• Of course, if you have a molecule with only one
nonpolar bonds (because it’s the same atoms), that
molecule will be a NONPOLAR MOLECULE
regardless of the shape
• Like H2
• Like ozone, O3
But what if the bonds are polar? Does
that mean the molecule is polar?
• Not necessarily….
Nonpolar Molecules
• Molecules with polar bonds do not always create polar
molecules.
• Example: CCl4
• Shape is tetrahedral.
• Because the polar bonds are spread out symmetrically in
space, this has the net effect of cancelling each other out.
• CCl4 is a nonpolar molecule.
• Again, whenever polar bonds are symmetrically arranged, they
produce nonpolar molecules.
• Another example: CO2
+
• Hey physics people, think of a molecule as being nonpolar
when the vectors add to zero 
• If the polar bonds are arranged asymmetrically, the
molecule is polar.
• For example, see how there are hydrogen atoms on
one side of the ammonia molecule and no
hydrogen atoms on the other side? POLAR
CHCl3 is commonly known as chloroform.
• Are the bonds polar?
Yes!
• Chlorine is more
electronegative than
carbon. (ΔEN=0.61)
• Carbon is more
electronegative than
Hydrogen. (ΔEN=0.30)
• Is this molecule polar?
• Yes! Because there are
different differences in
electronegativity (the
ΔEN’s are different)
FYI: anytime you have two
different atoms attached
to the same central atom,
the molecule will be polar.
• Just remember “SNAP”
• SNAP Symmetrical Nonpolar Asymmetrical Polar
• Molecular polarity is determined by the shape and
distribution of charge in the molecule. To make your life
easier, just look the atoms.
• If the noncentral atoms on the molecule are different, the molecule is
polar. Example: CHCl3
• If the atoms in the molecule are the same and arranged
symmetrically, the charges are balanced by each other. The
molecules are considered to be nonpolar. CH4
• However, if the molecule is asymmetrical, it is considered to be polar.
NH3
• So if it is lopsided, it is polar. If it is balanced, it is nonpolar.
You need
• A piece of paper and a pencil/pen
• Your chart with bond angles
Station Review/Notes
• You will complete a station review/notes activity
• You will work with your FACE partner
• If you don’t have a face partner, pair up with someone
else who also doesn’t have a face partner
• If there is an odd number, you can work in a group of 3
Station Review/Notes
• If there are two pages at a station
• If they are numbered (1 and 2), do 1 first
• If there are no numbers, do them in any order
• You can do the 8 stations in any order EXCEPT
• Do station 1 before station 2
• You will be
• Taking notes (if it’s stuff you know, don’t write it down; if you
didn’t remember it or it is new, take notes)
• Doing practice problems
• Learning information
• Reviewing information
• Stations 1,3,and 7 have answers on yellow paper hanging
on the far left board
• Work until bell rings; you should get done with at least 5
of the stations (we will finish next time)
Do not present the slides that
follow
Copy down the flow chart below
• Determine if the following are polar or nonpolar
•
•
•
•
•
•
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BI3
ClO2F
Carbonate
Phosphite
Water
Ammonia
Carbon dioxide