jwallach

1. How to identify if a substance contains ionic
or covalent bonds.
As with most things, this is not an absolute rule. There are
many exceptions.

2. Purpose
• The type of bonding present in a substance greatly influences
its properties. Additionally, it will determine how we name a
substance. For example, the systematic name of H2O is
dihydrogen monoxide, while the systematic name of Li2O is
lithium oxide – one has covalent bonds and uses the prefix di-
and the other has ionic bonds and does not use prefixes. For
these reasons, we need to be able to identify if a compound
presented to us contains ionic or covalent bonds.

3. If the substance contains a metal and one or
more non-metals, it is likely ionic.
• Some examples of ionic compounds
– NaCl
• Sodium is a metal and chlorine is a non-metal
– Fe(NO3)2
• iron is a metal and nitrogen and oxygen are non-metals
– ZnSO4
• Zinc is a metal and sulfur and oxygen are non-metals
– MgS
• Magnesium is a metal and sulfur is a non-metal

4. If the substance contains all non-metals, it is
likely covalent.
• Some examples of covalent compounds
– HCl
– C6H12O6
– CS2
– H2O

5. Important exception – ionic compounds containing
ammonium (NH4
+) do not have a metal.
• These compounds contain all non-metals; however, they contain ionic
bonds. The polyatomic ion NH4
+ is in the place of the metal.
– NH4Cl
– (NH4)2SO4

6. Pause and Practice
• Identify if each of the following is likely to have ionic bonds or covalent
bonds
– FeS
– SO2
– MgCO3
– NH4Cl
– CH4

7. Pause and Practice - Answers
• Identify if each of the following is likely to have ionic bonds or covalent bonds
– FeS
• Ionic – iron is a metal and sulfur is a non-metal
– SO2
• Covalent – both sulfur and oxygen are non-metals
– MgCO3
• Ionic – magnesium is a metal and carbon and oxygen are non-metals
– NH4Cl
• Ionic – ammonium is an exception to the metal rule and chlorine is a
non-metal
– CH4
• Covalent – both carbon and hydrogen are non-metals

8. Try the exercise.