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Where Mg (magnesium) is a metal and Cl (chlorine) is a non-metal.


               RULE III: In case compounds are formed from polyatomic ions then the ion is enclosed
               in a bracket before writing the number to indicate the ratio. But in case the number of
               polyatomic ion is one then there is no need for bracket.








               Since the number of polyatomic ion is one therefore no brackets are required.









               The formula for calcium hydroxide is Ca (OH) 2. The brackets around oh with subscript 2
               implies the presence of two hydroxyl group joined to one calcium atom.







































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