Principles of Chemistry · 2 question types
Past paper frequency (2018 to 2024)
This topic accounts for approximately 9% of your exam marks.
Ion formation, lattice structures and properties of ionic compounds tested consistently.
For Edexcel IGCSE, the charges of a fixed set of common ions must be learnt by heart.
| Ion | Charge | Example |
|---|---|---|
| Group 1 metal | 1+ | Li⁺, Na⁺, K⁺ |
| Group 2 metal | 2+ | Mg²⁺, Ca²⁺ |
| Group 3 metal | 3+ | Al³⁺ |
| Silver | 1+ | Ag⁺ |
| Copper(II) | 2+ | Cu²⁺ |
| Iron(II) | 2+ | Fe²⁺ |
| Iron(III) | 3+ | Fe³⁺ |
| Lead(II) | 2+ | Pb²⁺ |
| Zinc | 2+ | Zn²⁺ |
| Hydrogen | 1+ | H⁺ |
| Ammonium | 1+ | NH₄⁺ |
| Ion | Charge | Example |
|---|---|---|
| Group 5 non-metal | 3− | N³⁻ |
| Group 6 non-metal | 2− | O²⁻, S²⁻ |
| Group 7 non-metal | 1− | F⁻, Cl⁻, Br⁻, I⁻ |
| Hydroxide | 1− | OH⁻ |
| Nitrate | 1− | NO₃⁻ |
| Carbonate | 2− | CO₃²⁻ |
| Sulfate | 2− | SO₄²⁻ |