Lewis Structures
The Lewis Structure is a representation
of a molecule that shows how valence
electrons are arranged in atoms of a
molecule
Most important…Atoms achieve a noble gas
configuration diatomic fluorine
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Lewis Structures: Representing Valence Electrons in Atoms of a Molecule, Summaries of Chemistry
The concept of Lewis Structures, a method used to represent the arrangement of valence electrons in atoms of a molecule. It covers the rules for drawing Lewis Structures, including the noble gas configuration, single bonds, and octet rule. It also discusses exceptions and resonance structures.
Typology: Summaries
2021/2022
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Lewis Structures
The Lewis Structure is a representation
of a molecule that shows how valence
electrons are arranged in atoms of a
molecule
Most important…Atoms achieve a noble gas
configuration diatomic fluorine
Lewis Structure Rules
1. Only include the valence electrons
Count the total number in the compound
Represented by dots
2. Identify the central atom(s)
It will have the largest atomic
radii
It is generally the atom that is
most singular
3. Draw in single lines between the central atom(s) and the other atoms in the compound
These lines represent single bonds
Represents 2 electrons
Example : ( - )… C – 0
4. Add in single dots to the remaining atoms in the compound
These represent
unbonded electrons
- Make sure that the elements in the compound follow 1 of the following rules:
A. Duet rule
Only applies to H Forms stable molecules when it shares 2 electrons In effect, this gives H a filled 1 st valence shell
B. Octet Rule
Applies to most other elements Exceptions : B & Be (6), S (12)
6. Recheck the total number of valence electrons
Remember → 1 dot = 1 electron
1 line (-) = 2 electrons
If the # matches, you are done
If the # is too many, you will need to add
double or triple bonds
A. Double bond – involves sharing 2 pairs of electrons Represented by a double line (=) B. Triple bond – involves the sharing of 3 pairs of electrons Represented by a triple line (≡ )
7. Double check your work
If the total # of valence electrons does not
work out, go back to step 6
Examples : Single Bonds (Alkanes) Double Bonds (Alkenes) Triple Bonds (Alkynes)
Resonance
Sometimes it is possible for more than 1 Lewis
Structure to be drawn for a given molecule
Example : CO 2 ( 16 valence electrons) Note : The total number of valence electrons still add up Example : NO 3 ion ( 23 valence electrons) Note : Ions use brackets [ ] to symbol that they posses more electrons than they should Represented with double-sided arrows
Other resonance examples: Carbonate ion (CO 3 2 - ) Acetate ion (C 2
H
3
2
- )