Ionic Bonding

As well as sharing electrons, atoms can gain or lose electrons to give them a full outer shell. The number of protons is then diffrent from the number of electrons. 

The resulting particle has a charge and is called an ion.

When metal atoms react with non-metal atoms they transfer electrons to the non-metal atom.

Metal atoms lose electrons to become postive ions.

Non-Metal atoms gain electrons to become negative ions. 

When Metal atoms transfer electrons to non-metal atoms you end up with postive and negative ions.

These are attracted to each other by the strong electrostatic force of attratcion.

This is called ionic bonding.

The electrostatic force of attraction works in all directions, so many billions of ions can be bonded together in a 3D structure.

Formulae:

The formulae of an ionic substance can be worked out.

1. from its bonding diagram: for everyone magnesium ion there are two flourine ions 

2. from a lattice diagram: there are nine iorn ions.

Melting Points:

Ionic Substances have high melting points because the electrostatic force of attraction between oppositley charged ions is strong and so requires lots of energy to break.

Conductivity:

Solid ionic substances do not conduct electricty because the ions are fixed in postion and not free to carry charge.

When melted or dissolved in water, ionic substances do conduct electricty because the ions are free to move and carry charge.

Pure metals are often too soft to use as they are.

Adding atoms of a diffrent element can make the resulting mixture harder because the new atoms will be a diffrent size to the pure metal's atoms.

This will disturb the regular the regular arrangement of the layers, prevnting them from sliding over each other.

The harder mixture is called an alloy.