Start with electrons
Atoms are neutral: they have equal numbers of positive protons and negative electrons. Only outer-shell electrons take part in the bonding models in this topic. The nuclei stay intact.
Lesson 2.1 · AQA Combined Science
Atoms, ions and types of bonding
What is an ion?
An ion is an atom or group of atoms with an electrical charge. An atom that loses electrons becomes positive. An atom that gains electrons becomes negative. Magnesium loses two electrons to form Mg²⁺.
Three ways to bond
| Bonding | Usually between | What holds it together? |
|---|---|---|
| Ionic | Metal and non-metal | Strong electrostatic attraction between opposite ions. |
| Covalent | Non-metal atoms | A shared pair of electrons attracted to both nuclei. |
| Metallic | Metal atoms | Attraction between positive metal ions and delocalised electrons. |
Predict the ion charge
| Group | Electron change | Ion charge |
|---|---|---|
| 1 | Loses 1 | +1 |
| 2 | Loses 2 | +2 |
| 6 | Gains 2 | −2 |
| 7 | Gains 1 | −1 |
For these main-group ions, the new electron arrangement is like a noble gas: a full outer shell. Electrostatic means caused by electric charges. Opposite charges attract.
Remember
Lose electrons → positive. Gain electrons → negative. Ionic, covalent and metallic bonds are all strong.
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