Chemistry CN
Chemist:_______________
Date:_____________
Period:_____
Topic:________________________________________________________________________
Remember:
In a Lewis Structure:
 Only the ______________________ are involved
 Most atoms strive to get 8 e- in their outer principal electron
layer. This is the “_________________.”
 Each ______________represents 1 electron.
 Each ______________ represents 2 shared electrons in a
___________________ bond.
 Sometimes the lines are shown as dots
How to draw Lewis Structure for the 1. Count the valence e- available.
_________ electrons for negative charges.
OCl- (bleach) ion.
__________ electrons for positive charges
2. Draw a “skeleton” structure using single bonds (lines) for pairs of
shared electrons.
3. Distribute the rest of the e- around the atoms so each atom has
____ electrons.
There are 3 things that can occur with
your electrons on the central atom:
Important Tips:
 1. There are just enough e- to go around. Every atom has
______and H atoms have _______.
 2. If there aren’t enough e- to go around, then move a pair of
e- next to an existing single bond to make a double or triple
bond.
 3. If there are too many e-, then the atom may have an
“____________________.” Put the extra e- pairs on the
central atom.
 ___________ is usually a central atom, while H, O, and the
__________ are usually terminal atoms with ONLY one
single bond.
Chemistry CN
Chemist:_______________
Date:_____________
Period:_____
Topic:________________________________________________________________________
 The__________ atom listed in the chemical formula is
usually the central atom.
 Carbon always has 4 lines (4 covalent bonds) coming off of it.
Draw the Lewis Structure for CH3OH,
methanol.
Draw the Lewis Structure for the sulfite
ion, SO32-
Draw the Lewis Structure for the Nitrate
ion, NO3-
Exceptions to the Octet Rule:
Part 2: Predicting Molecular Geometry
(Shapes)
 Some _______________ elements don’t have 8 e- on the
central atom.
 Examples:
 Molecular shapes can be predicted using the Valence Shell
Electron Pair Repulsion, ______________ principle.
 All e- pairs try to get as ______________________ from each
other as possible.
 You must draw the Lewis structure before you can predict the
geometry.
 Add up the number of “________________” pushing away
from the central atom.
(continued)
Chemistry CN
Chemist:_______________
Date:_____________
Period:_____
Topic:________________________________________________________________________
 Each ___________________________ and atom(s) bonded to
the central atom, count as a “force.”
 Double or Triple bonds behave like just ______“force.”
The 3 basic “Repulsion Angles”
 2 Forces: make a _______________ molecule with _______
angles off the central atom.
 3 Forces: repel in a _______________ pattern with _______
angles.
 4 Forces: repel in a ________________ pattern with
_________ angles.
How do you tell if a molecule is “polar?”
What is the molecular geometry of
 A molecule is “___________________” when it has more
electrons on one side than on the other. This means it has a
negative side with more electrons and a positive side with less
electrons.
 Generally, if a molecule is perfectly ________________with
no unshared e- pairs, then it is non-polar.
 __________________ usually make it polar.
 If the ____________________ are different, then it's polar
(different charge on each end)
BF3
? Geometry:
Angle(s):
Polar/nonpolar:
What is the geometry of a water Geometry:
molecule? Angle(s):
Polar/nonpolar:
Chemistry CN
Chemist:_______________
Date:_____________
Period:_____
Topic:________________________________________________________________________
Summary: (3-4 GOOD sentences) On separate sheet of paper.