Ionic BondingOxford AQA IGCSE Chemistry: Revision notes
Section 1
What is ionic bonding?
Ionic bonding occurs between a metal and a non-metal. Atoms transfer electrons so that both end up with the electron arrangement of a noble gas (Group 0) — a full outer shell.
- The metal atom loses electrons, becoming a positively charged ion (cation)
- The non-metal atom gains electrons, becoming a negatively charged ion (anion)
Key termsioncationanion
Section 2
How does the charge relate to the group number?
The charge on a simple ion is related to the group number of the element in the periodic table:
| Group | Ion charge | Example |
|---|---|---|
| 1 | +1 | Na⁺ |
| 2 | +2 | Mg²⁺ |
| 6 | −2 | O²⁻ |
| 7 | −1 | Cl⁻ |
- Group 1 alkali metals react with non-metals to form ionic compounds where the metal ion has a single positive charge (+1)
- Group 7 halogens react with metals to form ionic compounds where the halide ion has a single negative charge (−1)
Key termsgroup number
Exam tip
Learn the pattern: metals in Groups 1–3 lose electrons to form positive ions matching their group number; non-metals in Groups 5–7 gain electrons to form negative ions equal to (8 − group number).
Section 3
How do we write ion symbols?
Ions are written in standard form, showing the symbol followed by the charge as a superscript, e.g.:
- Na⁺ — a sodium ion that has lost one electron
- Cl⁻ — a chloride ion that has gained one electron
- Mg²⁺ — a magnesium ion that has lost two electrons
All simple ions formed this way have the electron arrangement of the nearest noble gas.
Key termsstandard form
Must Know
- Ionic bonding involves the transfer of electrons from a metal atom to a non-metal atom
- Metal atoms lose electrons to form positive ions; non-metal atoms gain electrons to form negative ions
- Ions formed this way have the electron arrangement of a noble gas
- Ion charge relates to group number: Group 1 metals → +1, Group 7 halogens → −1
- Ions are written in standard form, e.g. Na⁺, Cl⁻
- Ionic bonding is one of three bonding types, alongside covalent (sharing) and metallic (delocalised electrons)
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