Bonding - Ionic

Ionic bonding is the type of bonding that occurs when metals combine with non-metals. During this type of bonding, electrons are transferred from metal atoms to non-metal atoms to form compounds. The metal atoms form positive ions and the non-metal atoms form negative ions. It is only the outermost electrons that are involved so it is important that you are confident working out the electron arrangement of the first twenty elements.

A compound that contains only one type of metal bonded to one type of non-metal is known as binary compound. For the exam, if you are asked to illustrate how ionic bonding works, you will only be asked to display your knowledge of this type of compound but be prepared for the examiners to ask about metals or non-metals that you may not have dealt with in lessons. If they do, you will be given the appropriate information that will enable you to apply your understanding. Stay calm and remember the basics.

Some of the ions involved in ionic bonding contain more than one element and are therefore called compound ions. These are exclusively made from non-metals e.g. SO₄^2- (the sulfate ion) or NO₃^- (nitrate ion). You don't need to know how or why they are formed, but you do need to know how they react and use that understanding to write the names and formulae of the new substances that are formed if you are studying for the higher tier. At high school, there is only one compound ion with a positive charge - the ammonium ion (NH₄⁺).

Ions have a small positive or negative electrostatic charge and it is these opposite charges attracting one another that holds the ions together to form a giant lattice. If sufficient numbers of ions are present, you see this lattice as a crystal, the shape of which depends on how the ions pack together.

Pure water is an insulator but will conduct electricity when it contains ions. This is because many ionic lattices come apart when the compound is added to water. The ions are free to move around and can move towards any electrodes that are placed in the water.