Question: which one of the following elements shows different oxidation states?
Answer: Element La shows only one oxidation state (+3), elements Eu exihibits two oxidation states (+2 and +3), element Gd exihibits only one oxidation state (+3) while the element Am exhibits a wide range of oxidation states (+2,+3,+4,+5 and +6) of which +3 is the most stable one.