Ionic bonding · GCSE Chemistry

Three types of bonding

Ionic bonding happens between metals and non-metals: oppositely charged ions attract.
Covalent bonding happens between non-metals: atoms share pairs of electrons.
Metallic bonding happens in metals and alloys: atoms share delocalised electrons.

When a metal reacts with a non-metal, electrons are transferred from the metal atoms to the non-metal atoms.
Metal atoms lose electrons to become positive ions; non-metal atoms gain electrons to become negative ions.
The ions have the electronic structure of a noble gas (a full outer shell).
Group 1 ions are +1, group 2 are +2, group 6 are −2 and group 7 are −1.
Dot and cross diagrams show the transfer: for example, sodium gives one electron to chlorine to form Na⁺ and Cl⁻.

An ionic compound is a giant structure of ions (a giant ionic lattice), like sodium chloride.
It is held together by strong electrostatic forces of attraction between oppositely charged ions. These act in all directions.
The formula shows the ratio of ions so the charges balance: Na⁺ and Cl⁻ give NaCl; Mg²⁺ and Cl⁻ give MgCl₂.
Diagrams have limitations: dot and cross diagrams don't show the 3D structure; ball and stick models show gaps between ions that aren't really there.

They have high melting and boiling points, because lots of energy is needed to break the many strong bonds.
They conduct electricity when melted or dissolved in water, because the ions are free to move and carry charge.
They do not conduct when solid, because the ions are held in fixed positions.

Ion: An atom or group of atoms with an electric charge because it has lost or gained electrons.
Ionic bond: The strong electrostatic attraction between oppositely charged ions.
Ionic compound: A compound made of positive and negative ions in a giant lattice.
Giant ionic lattice: A regular 3D arrangement of oppositely charged ions.
Electrostatic force: The force of attraction between opposite charges.
Dot and cross diagram: A diagram showing how electrons are transferred or shared, using dots and crosses.
Cation: A positive ion.
Anion: A negative ion.