What is the general formula of the halides formed by lanthanoids?
Answer & explanation
Correct answer: option 2
The general formula of the halides formed by lanthanoids is MX3.
The anhydrous halides MX3 can be made by heating the metal and halogen or by heating the oxide with appropriate ammonium halide.
Ln2O3 + NH4Cl → LnCl3 + 6NH3 + 3H2O