DRAWING LEWIS STRUCTURES
(ELECTRON DOT DIAGRAMS)
4.1
Drawing Lewis Structures
Step #1

Decide which atoms are
bonded The central atom
is usually more metallic, or
less electronegative not
usually oxygen, never
hydrogen
Drawing Lewis Structures
Step #2

Count the valence electrons
you have, add or subtract
electrons according to
charge of polyatomic ions.
Drawing Lewis Structures
Step #3

Place 2 electrons in
each bond between
atoms (remember
that they all will
have at least a
single bond)
Drawing Lewis Structures
Step #4
 Complete the octets of
the atoms attached to the
central atom, by adding
lone pairs. Place any
remaining electrons on the
central atom, in pairs
Drawing Lewis Structures
Step #5

If the central atom
does not have an
octet, form double or
triple bonds
Drawing Lewis Structures
Step #6

Draw the Lewis
structure and enclose
polyatomic ions within
square brackets
showing ion charge
Drawing Lewis Structures
Examples: HClO3 and SO3

Example CO3-2
Have = 1C + 3O + 2- charge
= 4 + 3(6) + 2
= 24
Need = 4(8)
= 32
# of bonds = (32-24)/2
=4
2-
O
O C O
Non-Octet Compounds

Some compounds will contain central atoms that
do not follow the octet rule.

The four possibilities for non-octet compounds
are:
1.
2.
3.
4.
Where more than 4 atoms are bonded to the
central atom such as PCl5.
A noble gas is participating in bonding such as
XeF4.
Where the central atom has less than 8 valence
electrons such as BH3.
Where molecules contain an odd number of
nonbonding electrons such as NO.
N O