Polyatomic Ions: Sample Problems

Try each one on paper first. Only then reveal the solution — reading a worked answer you never attempted teaches you almost nothing.

1. 1. Write the formula for calcium phosphate.

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2. 2. Name the compound (NH₄)₂SO₄.

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3. 3. How many oxygen atoms are in one formula unit of Al(NO₃)₃?

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4. 4. Write the formula for sodium dichromate.

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5. 5. Name the compound Ca(ClO)₂.

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Al says…

Learn them in families. Once you know sulfate is SO₄²⁻, sulfite is just one oxygen lighter. Same trick works for nitrate/nitrite and the chlorate family.