Ionic bonding · Year 10
When a metal reacts with a non-metal, electrons move from the metal atoms to the non-metal atoms. The metal atoms become positive ions and the non-metal atoms become negative ions, and each ion has a full outer shell. The oppositely charged ions attract each other strongly in every direction, building a giant ionic lattice.
Key facts
- Metal atoms lose their outer electrons to form positive ions; non-metal atoms gain electrons to form negative ions.
- Group 1 metals form 1+ ions, group 2 form 2+ and aluminium 3+. Oxygen and sulfur form 2− ions; the halogens form 1− ions.
- An ionic bond is the strong electrostatic attraction between oppositely charged ions.
- In the formula of an ionic compound the charges cancel out: Mg²⁺ and Cl⁻ make MgCl2.
- Dot-and-cross diagrams show the outer electrons: one atom’s electrons as dots and the other’s as crosses, with each ion in square brackets.
- Ionic compounds have high melting points, and conduct electricity only when melted or dissolved in water, when their ions can move.