Name _________________________
Lewis Dot structures of Ionic Compounds
Ionic compounds generally contain a metal and a nonmetal in the formula. The metal
cations come first in the formula, while the nonmetal containing anions are second in the
formula. The only exception to this is when the cation is the ammonium ion (NH4+),
which does not contain a metal.
There are two basic types of ionic compounds: (1) Binary compounds, or compounds
with just two types of atoms in the formula, i.e. NaCl; and (2) Terinary compounds, or
compounds that have three or more types of atoms in the formula. Generally the terinary
compounds result from the combination of a monoatomic cation (or ammonium ion) and
a polyatomic anion, i.e. Na2CO3.
To write the Lewis dot structure of a binary ionic compound simply write the Lewis dot
structure(s) of the cation(s), including brackets and the charge, followed by writing the
Lewis dot structure(s) of the anion(s), including brackets and charges. For example, the
Lewis dot structure of NaCl is shown in Figure 1a. In order to draw the Lewis dot
structures of polyatomic ions, simply follow the rule established for molecular
compounds, being sure to add or subtract electrons resulting from the charge of the ion,
as shown in Figure 1b for NH4Cl. Be sure to draw the Lewis structure for each ion in the
formula. For example in Li2O, there are two lithium ions and only one oxide ion.
..
[Na]+[:Cl:]
..
H
..
H-N-H + [:Cl:]
..
H
(a)
(b)
Figure 1. (a) NaCl and (b) Na2CO3.
Draw Lewis dot structures for the following ions.
1. F-
2. Na+
3. O2-
4. N3-
5. NH4+
6. BF4-
7. OH-
8. S2-
9. O22-
10. Mg2+
© Van Der Sluys, 2004
Name _________________________
Lewis Dot structures of Ionic Compounds
Identify the cation and anion in each of the following ionic compounds and draw the
Lewis dot structure for each compound.
11. Na2O
12. NH4F
13. NaOH
14. MgF2
15. Na2O2
16. LiF
17. NH4OH
18. CaCl2
19. Al(OH)3
20. CaO
© Van Der Sluys, 2004
Name _________________________
Answers
..
1. [:F:]
..
2. [Na]+
..
23. [:O:]
..
..
34. [:N:]
..
H
5. [H-N-H]+
H
..
+
.. :F: ..
:F-B-F:
.. ..
:F:
..
6.
..
7. [:O-H]
..
..
8. [:S:]
.. 2.. ..
9. [:O-O:]
.. .. 210. [Mg]2+
..
211. [Na]+ [Na]+ [:O:]
..
H
..
12. [H-N-H]+ [:Cl:]
..
H
..
+
13.
[Na] [:O-H]
..
..
.. 14. [Mg]2+ [:F:]
.. - [:F:]
..
.. ..
215. [Na]+ [Na]+ [:O-O:]
.. ..
..
16. [Li]+ [:F:]
..
H
..
17. [H-N-H]+ [:O-H]
..
H
..
..
18.
[Ca]2+ [:Cl:]
[:Cl:]
..
..
..
..
..
19. [Al]3+ [:O-H]
[:O-H]
[:O-H]
..
..
..
..
220. [Ca]2+ [:O:]
..
..
© Van Der Sluys, 2004
Lewis Dot structures of Ionic Compounds