Ionic compounds

What is an ionic bond

The electrostatic attraction between two oppositely charged ions

Structure of ions

Arranged in a crystal lattice - an orderly pattern of ions

Melting point

Very high melting point due to the strength of an ionic bond - very strong due to the complete donation/transfer of e- , not just sharing

What affects melting point

Charge - the higher the charge the higher the melting point because the attraction is also higher. Eg. NaCl has a lower boiling point than MgO due to the charges

Atomic radius - The size of an atom affects it’s distance of e- to the nucleus, so a smaller ion can pack more tightly in a lattice and the distance between two ions is smaller, thus increasing the attraction and making it harder to break = higher melting point.

What is lattice enthalpy

A measure of energy required to break the ionic bonds and convert the substance into a gaseous state

Conductivity?

In a solid state - no, it’s a poor conductor since electrical conductivity requires movement of ions which carry a charge. When melted, though, the ions are free from the lattice structure and can move around carrying charged.

Solubility

Very soluble in water when dissolved from structure as the ions are charged and can be attracted to the water molecules as the water molecules are polar (O is attracted to the positive ions, H is attracted to the negative ions)

Brittle

They tend to be brittle because if you strike one part of the lattice structure, it can move over and force the negative to be with the negative and positive to be with positive ions , which repulse each other and force movement away

Volatility

Volatility - ease of evaporation. Ionic materials have an incredibly high boiling point so they have very low volatility due to their strength. Can be affected by charge and size, again.