3) Ionic Compounds

What structure do ionic compounds form?

Ionic compounds form a giant ionic lattice, with ions in a closely packed, regular arrangement.

What holds the ions together in a giant ionic lattice?

Electrostatic forces (ionic bonds) hold oppositely charged ions together in a giant ionic lattice.

What does a ball and stick model show in ionic compounds?

It shows the regular pattern of the lattice and the relative sizes of ions, but only shows the outer layer of the compound.

Why do ionic compounds have high melting and boiling points?

Because the strong ionic bonds between ions require a lot of energy to break.

Why don’t solid ionic compounds conduct electricity?

In solids, the ions are held in place and cannot move to conduct electricity.

When do ionic compounds conduct electricity?

When melted (in a molten form) or dissolved in water, the ions are free to move and can carry an electric charge.

How can you find the empirical formula of an ionic compound?

From a dot and cross or 3D lattice diagram, count the ions, balance their charges, and write the formula so the overall charge is zero.

What is the empirical formula of potassium oxide (K₂O)?

K₂O. Potassium forms 1⁺ ions and oxygen forms 2⁻ ions, so two potassium ions balance the charge of one oxide ion.

What happens when an ionic compound dissolves in water?

The ions separate and are free to move, allowing the compound to conduct electricity.

What is one limitation of the ball and stick model?

It doesn’t show the gaps between ions accurately, as in reality, there are no gaps in the lattice.