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Polyatomic Nomenclature

Naming Polyatomic and Writing Formulas from Names

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Polyatomic IonsIons that are made up of more than one element

The elements stay together and act as one unit in chemical reactions

Together the elements still carry a charge

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KomperdaWriting Formulas From Names

1. Identify the Anion

2. Identify the Cation

3. Determine the total number of cations and anions needed to make the formula electrically neutral (these become the subscripts)

4. You must use parenthesis if there is more than one polyatomic ion needed for the formula

5. Write the formula, putting the cation first, then the anion

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How does that work?Sodium Phosphate: Na+ + PO4

3- = Na3PO4

Magnesium Phosphate: Mg2+ + PO43- = Mg3(PO4)2

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Polyatomic Ionic Compounds

1. Identify and name the cation

2. Identify and name the anion (often the polyatomic ion)

3. Put the names together, naming the cation first, then the anion