Lewis Dot Diagrams
A Lewis dot structure is like a simplified electron energy level model. The Lewis structure contains
the element symbol with dots representing electrons. The only electrons shown are those on the
outer energy level or valence electrons. The electrons are placed around the element symbol, one at
a time, clockwise or counterclockwise, and then grouped in pairs as more electrons are added.
Covalent Bonding
Lewis dot structures can also be used to show the bonded
atoms in a molecule. The two dots together between the
Hydrogen atoms represent the electrons in the covalent bond
between the hydrogen atoms. The line is a short-hand version
of the two dots.
The Lewis dot structure for water shows the
electron from hydrogen and an electron
from oxygen being shared in a covalent
bond. The other four valence electrons in
oxygen are in pairs at the bottom. The lines
are a short-hand version of the two dots
representing the covalent bonds.
The two pairs of dots between the Oxygen
atoms represent the double covalent bond
in the oxygen molecule. The two lines are a
short-hand version of the two pairs of dots.
The two pairs of dots between the C
and the Os represent the double
covalent bond between the carbon and
each oxygen atom in the carbon
dioxide molecule.
The two sets of two lines are a shorthand version to show the two double
covalent bonds.
When sodium (salt) loses its only valence
electron to become an ion, the Lewis
structure shows it with no dots (electrons).
The Na and Cl are near each other but the
two dots from the Cl should not be
interpreted as a covalent bond.
Reflection Questions:
1. How are electrons arranged around the nucleus of an atom?
2. What charge do electrons carry?
3. Describe the energy levels of electrons around a nucleus.
4. How do you read a Lewis Dot Structure? (What do the dots represent?)
5. How can Lewis Dot Structures help you visualize how electrons interact?