Electron Dot Structure
also called Lewis Dot Structure
Arranging the dots…
Dots are placed around a symbol to
indicate the number of valence eHow many dots may be present?
Duet or Octet Rule?
Arranging the dots…
Dots are used to indicate covalent
bonding.
For what type of element will we be
drawing electron dot structures?
What types of compounds will be
illustrated?
Arranging the dots…
6 2
X
3
7
X
5
1
4 8
Dots can be rearranged to
accommodate bonding illustration.
Arranging the dots for an atom…
H
Cl
Arranging the dots for a molecule…
H
Cl
H Cl
Arranging the dots and lines for a
molecule…
Replace bonding pairs with a line,
but always show the lone pairs of electrons.
H Cl
Notice that each atom is obeying its proper rule…
duet or octet…
upon completion of the dot structure.
Arranging the dots for water…
H
H
O
Final structure for water…
H O
H
Arranging the dots for
carbon dioxide…
C
O
O
Arranging the dots for
carbon dioxide…
O C O
Arranging the dots for
carbon dioxide…
O C O
Final structure for
carbon dioxide…
O C O
Arranging the dots for
carbon monoxide…
C
O
Arranging the dots for
carbon monoxide…
C O
Arranging the dots for
carbon monoxide…
C O
How many electrons does the oxygen
have around it?...the carbon?
Since O is happy, and C is not, we move
electrons around to keep everyone happy.
Arranging the dots for
carbon monoxide…
C O
This is a coordinate covalent bond—
it is made when one atom contributes
both electrons to a covalent bond.
Final structure for
carbon monoxide…
C O
Avoiding the trickiness…
The Kelter Method of drawing electron dot
structures
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saves a lot of grief
enables the successful drawing of electron
dot structures without the hassle of figuring
out which electrons go where
has exceptions, but they are logical
The Kelter Method
Determine the number of happy e- in the
entire molecule or ion.
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Happy electron number depends upon
whether the atom obeys the duet or octet rule
Determine the number of owned e- in the
entire molecule or ion.
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Owned electron number depends upon the
number of valence electrons that the atom
has
The Kelter Method
Subtract the number of owned e- from the
number of happy e- and divide that
difference by two…this will equal the
number of bonds in the molecule or ion.
#happy e- - #owned e- = #bonds
2
The Kelter Method
Place the appropriate number of bonds
around the central atom.
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Central atom is the one that occurs one time
in the molecule or ion. It is usually carbon if
carbon is present.
Attach the perimeter atoms and make
them all happy (obey the appropriate rule)
by placing electron dots around them.
The Kelter Method
Account for all of the owned e- that you
originally indicated, and add any leftovers
to the central atom.
If you are dealing with a polyatomic ion,
place brackets around the formula and put
the charge outside of the brackets.
The Kelter Method
Multiple bonds will be blatantly indicated
by the Kelter Method.
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If the Kelter Method tells you that you need
more bonds than you think you can possibly
have in the molecule or ion, then there will be
at least one multiple (double or triple) bond in
the molecule or ion.
The Kelter Method
Exceptions to the method will be
exceptions to the duet or octet rule…that
is, holding more than 2 or more than 8 earound a central atom.
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If the Kelter Method tells you that you need
fewer bonds than you know you can have in
the molecule or ion, then it will be an
exceptional situation.
The Kelter Method…H2O
#happy e- = 12
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Each H wants how many to be happy? 2
The O wants how many to be happy? 8
#owned e- = 8
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Each H already owns how many? 1
The O already owns how many? 6
12 – 8 = 2 bonds
2
The Kelter Method…H2O
Oxygen is the central atom…it only
appears one time.
O
Place two bonds around the central atom
as indicated by the Kelter Method
The Kelter Method…H2O
Attach the perimeter atoms…in this case
the two hydrogen atoms.
H O H
Make the perimeter atoms happy...
Each hydrogen atom wants two electrons, and
They already have two electrons…
no dots need to be added
The Kelter Method…H2O
Account for all of the owned electrons by
adding electrons to the central atom.
H O H
There were 8 owned electrons in this molecule…
Four are accounted for with the bonding lines…
Add the other 4 electrons around the central atom.
The Kelter Method…CO2
#happy e- = 24
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The C wants how many to be happy? 8
Each O wants how many to be happy? 8
#owned e- = 16
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The C already owns how many? 4
Each O already owns how many? 6
24 – 16 = 4 bonds
2
The Kelter Method…CO2
Carbon is the central atom…it only
appears one time.
C
Place four bonds around the central atom
as indicated by the Kelter Method
The Kelter Method…CO2
Attach the perimeter atoms…in this case
the two oxygen atoms.
O C O
Make the perimeter atoms happy...
Each oxygen atom wants 8 electrons, and
they already have 4 electrons…
4 dots need to be added to each oxygen
The Kelter Method…CO2
Account for all of the owned electrons by
adding electrons to the central atom.
O C O
There were 16 owned electrons in this molecule…
All 16 are accounted for with the bonding lines
and dots around the O’s…and all are happy.
The Kelter Method…CO
#happy e- = 16
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The C wants how many to be happy? 8
The O wants how many to be happy? 8
#owned e- = 10
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The C already owns how many? 4
The O already owns how many? 6
16 – 10 = 3 bonds
2
The Kelter Method…CO
There is no true central atom since there
are only two atoms.
C
Place three bonds next to the C atom
as indicated by the Kelter Method
The Kelter Method…CO2
Attach the O atom.
C O
Make each atom happy...Each atom wants
8 electrons, and they already have 6 electrons…
2 dots need to be added to each atom…
Account for all owned electrons.
The Kelter Method…OH1#happy e- = 10
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The O wants how many to be happy? 8
The H wants how many to be happy? 2
#owned e- = 8
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The O already owns how many? 6
The H already owns how many? 1
And the 1- charge tells you? 1 more e- is owned
10 – 8 = 1 bond
2
The Kelter Method…OH1There is no true central atom since there
are only two atoms.
O
Place one bond next to the O atom
as indicated by the Kelter Method
The Kelter Method…OH1Attach the H atom.
O H
Make each atom happy...The O wants 8 e-, and
the H wants 2 e-…The O and the H already
have 2 e-…6 dots need to be added to the O atom
Account for all owned electrons.
The Kelter Method…OH1Add brackets around the ion.
1-
O H
Place the charge of the ion outside
of the brackets.
The Kelter Method…OH1So, where did the extra electron
originate?
1-
Na
O H
1+
Na
Maybe a sodium atom was strolling by…and
donated an electron to the cause.
The Kelter Method…CO32#happy e- = 32
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The C wants how many to be happy? 8
Each O wants how many to be happy? 8
#owned e- = 24
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The C already owns how many? 4
Each O already owns how many? 6
And the 2- charge tells you? 2 more e- are owned
32 – 24 = 4 bonds
2
The Kelter Method…CO32Carbon is the central atom…it only
appears one time.
C
Place four bonds around the central atom as indicated by
the Kelter Method, but you only have 3 perimeter atoms…
The Kelter Method…CO32-
Attach the O atoms.
O
C
O
O
Make each O atom happy with 8 e-. Two O atoms already
have 2 e- and one O atom has 4 e- …6 dots need to be
added to two O atoms and 4 dots need to be added to
one O atom. Account for all owned electrons.
The Kelter Method…CO32Add brackets around the ion.
O
C
2-
O
O
Place the charge of the ion outside
of the brackets.
The Kelter Method…BI3
#happy e- = 26
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The B wants how many to be happy? 2
Each I wants how many to be happy? 8
#owned e- = 24
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The B already owns how many? 3
The I already owns how many? 7
26 – 24 = 1 bond
2
The Kelter Method…BI3
Boron is the central atom…there is no way
only one bond can accommodate 3 I’s!
So, override the Kelter Method
B
Place the number of bonds around the central atom that
will take care of all of the perimeter atoms…
The Kelter Method…BI3
Attach the perimeter I atoms.
I
B
I
I
Make each I atom happy with 8 e-. Each I atom already
has 2 e- …6 dots need to be added to each I atom
Now, practice bunches
Draw the electron dot structures of each
molecule or ion on the practice sheet on a
separate sheet of paper in your notebook.
Take your time with it.
Use the Kelter Method to help you.