Designed by Koen, my 4 yr old son for daddy.

Designed by Koen, my 4 yr old son for daddy.

Monday, August 3, 2009

Differentiating Ionic and Covalent Compounds

A common question asked by my students all the time, how do you know if a substance is an ionic or covalent compound?

The general rule is basically very simple and i am sure your teachers have mentioned many times.

Ionic compounds - formed by substances that is made up with positive and negative ions.
The EASIEST method to decide if a substance is ionic basically is to look at the formula of the compound. For example, magnesium chloride, basically made up of magnesium ion (metallic) and chloride ion (non-metallic). So to recognize an ionic compound, look out for a metal and a non-metal in formula. This however is just a general guide as there are exception cases.

For example, a compound like ammonium chloride, NH4Cl. Notice there are no metals, in ammonium chloride but it is still considered an ionic compound. Reason is because it is made up of the positive ammonium ion and negative chloride ion. However, it is still quite safe to to identify ionic by the metal - non metal rule.

Finally for covalent substances, its the easiest to identify. As long as the substance does not contain any metals it can be taken to be a covalent substance. That of course taking into account the annoying ammonium based substances which defy this rule.


Entry by
Json Lim

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