Naming Ions and Ion Radicals

By Dr. Donald G. McGahan
Published: September 15, 2008
Modified: March 11, 2016

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A single element (or a group of elements) with an electrical charge is called an ion. Ions which are positively charged are called cations, while those ions with a negative charge are anions. If an ion is not a single element but a group of elements such as (SO42-) this may be spoken of as a radical. 

Naming of radicals and compounds

Three suffixes are commonly used to denote the chemical state. These suffixes and rules for names of the compounds follow and should be learned.

  1. “ide” – Refers to the lowest negative valence state of an element. The negative ion in this case is always a single element, and is not combined with oxygen. Examples are H2S (hydrogen sulfide) and NaCl (sodium chloride).
  2. “ite” – Refers to the valence of some element combined with oxygen to form an ion but this element is not in its highest possible valence. For example, SO33-, has sulfur in a +4 valence but S can in some instances have a +6 valence. So this anion with S in a +4 valence is named “sulfite.”
  3. “ate” – Refers to some element combined with oxygen to form an anion. The particular element is in its highest valence state. (Example, SO42-, sulfate has sulfur in a +6 state, its highest oxidation).
  4. For cations (positive ions) having two valence states, the higher valence is “ic” and the lower valence is “ous”. Thus Cu+ is cupprous and Cu++ (or Cu2+) is cupric or Fe++ (or Fe2+) is ferrous and Fe+++  (or Fe3+) is ferric.
  5. To name compounds, use the element name of the cation plus the name of the anion.
    • NaNO3 is sodium nitrate
    • CuS is cuppric sulfide or Cu (II) sulfide
    • CaO is calcium oxide
    • Na2SO3 is sodium sulfite
    • NCl is ammonium chloride
    • FeO is ferrous oxide or Fe (II) oxide
    • K2CO3 is potassium carbonate

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