Common Ions (Edexcel IGCSE Science (Double Award))
Revision Note
Written by: Stewart Hird
Reviewed by: Lucy Kirkham
Common ions
How to deduce the charge of an ion
Find the number of electrons in the outer electron shell
Find out if it is easier for the atom to gain electron or to donate electron (in most cases atoms that have fewer than four electrons, donate electrons and atoms that have more than 4 electrons, receive electrons)
Atoms that gain electrons become negative ions and atoms that donate electron forms positive ion
You also need to learn the formula of compound ions, that is, ions made from more than one element
Common ions with a positive charge
Ion | Charge / formula |
|---|---|
Group 1 metals | 1+ (E.g. Na+) |
Group 2 metals | 2+ (E.g. Mg2+) |
Group 3 metals | 3+ (E.g. Al3+) |
Silver | Ag+ |
Copper(II) | Cu2+ |
Iron(II) | Fe2+ |
Iron(III) | Fe3+ |
Lead(II) | Pb2+ |
Zinc(II) | Zn2+ |
Hydrogen | H+ |
Ammonium | NH4+ |
Common ions with a negative charge
Ion | Charge / formula |
|---|---|
Group 5 non- metals | 3- (E.g. N3-) |
Group 6 non- metals | 2- (E.g. O2-) |
Group 7 non- metals | 1- (E.g. Cl-) |
Hydroxide | OH- |
Carbonate | CO32- |
Nitrate | NO3- |
Sulfate | SO42- |
Examiner Tips and Tricks
You must know the charges of all the ions shown in the above tables.
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