Common Ions (Edexcel IGCSE Chemistry)
Exam board Pearson Edexcel · IGCSEUpdated 2024-08-21
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Work through it step by step — key points, depth layers, a worked example and self-checks.
Spec point — know the charges of these ions: • metals in Groups 1, 2 and 3 • non-metals in Groups 5, 6 and 7 • Ag+, Cu2+, Fe2+, Fe3+, Pb2+, Zn2+ • hydrogen (H+), hydroxide (OH– ), ammonium (NH4 +), carbonate (CO3 2– ), nitrate (NO3 - ), sulfate (SO4 2– ).
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- |
Exam Hint You must know the charges of all the ions shown in the above tables.
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