A chemical ion is a charged particle. For example the magnesium ion, Mg2+ and the oxide ion, O2-have respective charges of 2+ and 2-
Other common examples of charged particles are the sodium ion, Na+ and the chloride ion, Cl-
Metals produce positve ions. eg. magnesium ion, Mg2+
Non-metals produce negative ions. eg. oxide ion, O2-
The charge of many ions is related to their position in the periodic table. See the table below.
Group I metals produce ions of a charge of +1.
Group II metals produce ions of a charge of +2 and so on.
Charges of metallic and non-metallic ions
|Lithium, Li+||Beryllium, Be2+||Nitride, N3-||Oxide, O2-||Fluoride, F-|
|Sodium, Na+||Barium, Ba2+||Aluminum, Al3+||Phosphide, P3-||Sulfide, S2-||Chloride, Cl-|
|Potassium, K+||Calcium, Ca2+||Bromide, Br-|
Ions can be divided into two groups based upon their charges.
An cation is a positively charged ion. Metallic elements produce positive ions. Examples of cations include potassium, K+ and calium, Ca2+
An anion is a negatively charged ion. Non-metallic elements produce negative ions. Examples of anions include oxide, O2- and nitride, N3-
The charges are due to a shortage or excess number of electrons in an atom.
Metallic elements have a tendecy to lose electrons in their valence or outer shell and produce postive ions. Metal atoms have either 1, 2 or 3 electrons in their valence shell which are lost in a chemical reaction.
The sodium atom loses one electron producing a positive sodium ion.
Na → Na+ + e−
Non metallic elements have a tendecy to gain electrons in their valence or outer shell and produce negative ions. Non metallic atoms have either 5, 6 or 7 electrons in their valence shell. They gain electrons in a chemical reaction.
A chlorine atom gains one electron producing a negative chlorine ion.
Cl + e− → Cl−