Ions and Ion Radicals
By Dr. Donald G. McGahan
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.
- "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).
- "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.”
- “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).
- 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.
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