Writing Lewis Structures for
Molecular (Covalent) Compounds
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sketch arrangement of atoms (determine
central atom)
determine number of valence eplace two e- in each bond
complete octets on non-central atoms
place any remaining e- on central atom
IF central atom has less than an octet,
form multiple bonds
Drawing Lewis Structures
Draw the Lewis structure for the NO21- ion.
First, determine the atomic arrangement.
O
N
O
Next, determine the total number of valence
electrons.
5 electrons from the N
6 electrons from each O for 12
more electrons
1 additional electron because it is a
monoanion
18 total valence electrons
Use the electrons to make electron-pair
bonds between the central and outer atoms.
O
N
O
18 - 4 = 14 electrons remain
Complete the octet of each outer atom.
..
N
..
O
..
..
..
O
..
14 - 12 = 2 electrons remaining
If there are any remaining electrons, put
them on the central atom.
..
..
N
..
O
..
..
..
O
..
All of the valence electrons have now
been used.
If, and only if, the central atom has fewer
than eight electrons, complete its octet by
using nonbonding electron pairs from outer
atoms to make multiple bonds.
..
..
N
..
O
..
..
..
O
..
In the final Lewis structure, each atom
should have a complete octet of electrons.
If it is an ion, indicate the charge outside
of brackets.
..
..
N
..
O
..
..
O
..
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