Sodium chloride (NaCl):
* Ionic bonding: NaCl consists of a strong ionic bond between positively charged sodium ions (Na⁺) and negatively charged chloride ions (Cl⁻). These ions are arranged in a crystal lattice structure.
* High melting point: The electrostatic forces of attraction between the oppositely charged ions are very strong. To melt NaCl, you need to overcome these strong forces, requiring a lot of energy. This explains its high melting point of 801 °C.
Iodine (I₂):
* Covalent bonding: Iodine exists as diatomic molecules (I₂) held together by weak intermolecular forces known as van der Waals forces. These forces arise from temporary fluctuations in electron distribution.
* Low melting point: The van der Waals forces are much weaker than the ionic bonds in NaCl. Therefore, less energy is needed to overcome these forces and separate the iodine molecules, resulting in a low melting point of 113.7 °C.
In summary:
* Strong ionic bonds: High melting point (NaCl)
* Weak van der Waals forces: Low melting point (I₂)
