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How to Tell if a Compound Is a Polyatomic Ion or a Binary Ion

Identifying compounds as covalent or ionic in nature helps a chemist determine what chemical reactions may take place. Covalent compounds react with each other forming new compounds, whereas ionic compounds react by associating with other ions. Oxidation-reduction reactions are a type of reaction where ionic compounds break apart into ions and electron pass from one ion to another and result in new ions or compounds forming. Binary ionic compounds are comprised of two different elements. One of the ions is usually a metal ion and the other a non-metal. Compounds that break apart and form an ion composed of more than one element are polyatomic ions.

Things You'll Need

Periodic table

Instructions

- 1
  Determine if a compound is covalent of ionic in nature. Covalent compounds form from non-metal atoms. Compounds that are ionic compounds form from a metal ion and a non-metal ion.
- 2
  Count the number of different elements in the ionic compound. If the number of different element atoms in the compound doesn't exceed two, the compound is a binary ionic compound. Ionic compounds containing more than three different elements are ionic compounds that possess a polyatomic ion. For example, sodium chloride contains two elements and is a binary ionic pair, whereas sodium carbonate contains three elements and contains a polyatomic ion with carbon and oxygen making up the polyatomic ion.
- 3
  Examine the name of the compound. Compounds that end in --ate and --ite are always polyatomic ions. If the compound ends in --ide and only contains two elements, the ionic compound is a binary ionic pair like sodium chloride. Sodium hydroxide ends in --ide but has three elements in the compound so it must possess a polyatomic ion.

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