CHEM 1170 - Key Polyatomic Ions

Halogen Oxyanions Nomenclature and Formulas

• Halogen oxyanions follow systematic naming patterns according to the relative number of oxygen atoms bound to the halogen element, each carrying a net charge of $-1$:

  • Prefix/Suffix Hypo-…-ite: Represents the oxyanion with 1 oxygen atom.
  • Suffix …-ite: Represents the oxyanion with 2 oxygen atoms.
  • Suffix …-ate: Represents the standard base oxyanion with 3 oxygen atoms.
  • Prefix/Suffix Per-…-ate: Represents the oxyanion with 4 oxygen atoms.

• Chlorine Oxyanions:

  • Hypochlorite: $ClO^-$
  • Chlorite: $ClO_2^-$
  • Chlorate: $ClO_3^-$
  • Perchlorate: $ClO_4^-$

• Bromine Oxyanions:

  • Hypobromite: $BrO^-$
  • Bromite: $BrO_2^-$
  • Bromate: $BrO_3^-$
  • Perbromate: $BrO_4^-$

• Iodine Oxyanions:

  • Hypoiodite: $IO^-$
  • Iodite: $IO_2^-$
  • Iodate: $IO_3^-$
  • Periodate: $IO_4^-$

Nitrogen, Sulfur, and Phosphorus Oxyanions

• Nitrogen Oxyanions:

  • Nitrite: $NO_2^-$
  • Nitrate: $NO_3^-$

• Sulfur Oxyanions:

  • Sulfite: $SO_3^{2-}$
  • Hydrogen Sulfite: $HSO_3^-$
  • Sulfate: $SO_4^{2-}$
  • Hydrogen Sulfate: $HSO_4^-$

• Phosphorus Oxyanions:

  • Phosphate: $PO_4^{3-}$
  • Hydrogen Phosphate: $HPO_4^{2-}$
  • Dihydrogen Phosphate: $H_2PO_4^-$

Additional Common Polyatomic Ions

• Carbon Polyatomic Ions:

  • Carbonate: $CO_3^{2-}$
  • Bicarbonate: $HCO_3^-$

• Nitrogen Polyatomic Ions:

  • Ammonium: $NH_4^+$
  • Cyanide: $CN^-$

• Oxygen Polyatomic Ions:

  • Hydroxide: $OH^-$
  • Peroxide: $O_2^{2-}$

Element Symbols and Polyatomic Ions Reference Guide