Why do metals have high boiling points?

Metals have high boiling points due to the strong metallic bonds that hold their atoms together.

Metals are made up of a lattice of positive ions surrounded by a 'sea' of delocalised electrons. This structure is often referred to as a 'metallic bond'. The strength of the metallic bond is determined by the number of delocalised electrons, which is why metals generally have high melting and boiling points.

The delocalised electrons are free to move throughout the structure, creating a strong bond between the positive ions. This bond is very difficult to break, which is why a lot of energy is required to change the state of a metal from solid to liquid or from liquid to gas. This energy is what we measure as the boiling point. The more energy required, the higher the boiling point.

For example, consider sodium and magnesium. Sodium has only one delocalised electron per atom, while magnesium has two. This means that the metallic bonds in magnesium are stronger than in sodium, and so magnesium has a higher boiling point.

Furthermore, the size of the ions also affects the strength of the metallic bond. Smaller ions can pack closer together, which strengthens the bond and increases the boiling point. For instance, aluminium ions are smaller than sodium ions, so aluminium has a higher boiling point than sodium.

In summary, the high boiling points of metals can be attributed to the strong metallic bonds that hold their atoms together. The strength of these bonds is influenced by the number of delocalised electrons and the size of the ions.