CAIE A-Level Chemistry 2.3.1 Ionic Formulae and Oxidation Numbers

Practise combining ion charges into neutral formulae and using periodic position or known ions to assign oxidation numbers.

Exam points

predict simple monatomic ion charge from periodic-table position where appropriate
combine ions in the smallest whole-number ratio so total positive and negative charge is zero
recall the specified common polyatomic ions and preserve brackets when more than one ion is required

[Maximum number: 1]

Species such as $\mathrm{NH}_{4}{ }^{+}, \mathrm{CO}_{3}{ }^{2-}$ and $\mathrm{PO}_{4}{ }^{3-}$ are examples of molecular ions.

There are many naturally occurring hydrated compounds that contain the anion $\mathrm{PO}_{4}{ }^{3-}$ .

Name the anion $\mathrm{PO}_{4}{ }^{3-}$ .

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