Why Melting and Boiling Points of Iron(II) Chloride are Higher then Iron(III) Chloride? - QS Study
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Melting and Boiling Points of Iron(II) Chloride (FeCl2) are Higher then Iron(III) Chloride (FeCl3):

If a metal atom forms several cations, then the cation with lowest charge will have least polarizing power and with the increase of charge the polarizing power increases.

For example iron forms two cations Fe2+ and Fe3+. Due to higher charge on Fe3+ it has higher polarizing power than Fe2+ ion, and hence its compounds have more covalent character.

Therefore the melting point of anhydrous FeCl3 (306°C) is less than that of anhydrous FeCl2 (670″C). Due to the same reason, the boiling point of FeCl2 is higher than FeCl3.