Provide an example of the melting point trend and bonding in Period 3 elements.

The melting point trend in Period 3 elements increases from sodium to silicon, then decreases.

The melting point trend in Period 3 elements can be explained by the bonding present in each element. Sodium and magnesium have metallic bonding, which involves a sea of delocalized electrons surrounding positively charged metal ions. This results in a relatively low melting point as the metallic bonds are relatively weak.

Aluminium has a giant metallic structure, where each aluminium atom is bonded to eight neighbouring atoms. This results in a stronger metallic bond and a higher melting point.

Silicon has a giant covalent structure, where each silicon atom is bonded to four neighbouring atoms through strong covalent bonds. This results in an extremely high melting point as a lot of energy is required to break these strong bonds.

Phosphorus, sulfur, chlorine and argon have simple molecular structures, where the molecules are held together by weak intermolecular forces. As a result, they have relatively low melting points compared to the previous elements in the period.

In conclusion, the melting point trend in Period 3 elements can be explained by the type of bonding present in each element. Metallic bonding results in a relatively low melting point, while giant metallic and covalent structures result in higher melting points. Simple molecular structures have relatively low melting points due to weak intermolecular forces.