Forming ionic bonds

Positive and negative ions form when a metal reacts with a non-metal, by transferring electrons. The oppositely charged ions are strongly attracted to each other, forming ionic bonds.

An explanation of ionic bonding

Dot and cross diagrams

A dot and cross diagram shows the transfer of electrons from metal atoms to non-metal atoms. The electrons from one atom are shown as dots, and the electrons from the other atom are shown as crosses. For example, when sodium reacts with chlorine, electrons transfer from sodium atoms to chlorine atoms. The diagrams show two ways of representing this electron transfer.

The outer electron from a sodium atom transfers to the outer shell of a chlorine atomThe outer electron from a sodium atom transfers to the outer shell of a chlorine atomThe electron transfer in sodium chlorineThe electron from a sodium atom transfers to a chlorine atom

Modelling ionic bonding

The slideshow shows dot and cross diagrams for the ions in sodium chloride, magnesium oxide and calcium chloride.

Structures of a sodium atom and a chlorine atom.

1. Ionic bonding in sodium chloride

Question

Draw a diagram, with outer electrons only, to show how the electrons are transferred when magnesium chloride is formed from its elements.

Diagram of the electron transfer in making magnesium chloride.