FeI3 Compound Classification: Type 1 vs. Type 2 Explained

FeI3 is a type 2 compound.

In a type 2 compound, the metal ion has a high charge and a small size, which results in a high charge density. This high charge density polarizes the halide ions, causing them to become distorted and form covalent bonds with the metal ion. The covalent bonds between the metal ion and the halide ions are stronger than the ionic bonds between the metal ion and the halide ions in a type 1 compound, which results in a higher melting point and boiling point for type 2 compounds.

FeI3 is a type 2 compound because the Fe3+ ion has a high charge (3+) and a small size (0.64 Å). This high charge density polarizes the I- ions, causing them to become distorted and form covalent bonds with the Fe3+ ion. The covalent bonds between the Fe3+ ion and the I- ions are stronger than the ionic bonds between the Fe3+ ion and the I- ions in a type 1 compound, which results in a higher melting point (947 °C) and boiling point (1806 °C) for FeI3.