Identify the correct statements from the following : I. The ionic radius of ( Pr ³⁺, Dy ³⁺ ) and ( Sm ³⁺ ) follow the order, ( Sm ³⁺ > Pr ³⁺ > Dy ³⁺ ). II. ( Eu ²⁺ ) acts as strong reducing reagent. III. Pu exhibits +7 oxidation state.

Step-by-step solution

(i) The ionic radius of lanthanoids follow the following relation: Ionic radius ( 1 atomic number ) Atomic number ((Z) ) for ( Pr =59 ) Atomic number ((Z) ) for ( Sm =62 ) Atomic number ((Z) ) for (D y=66 ) and has ionic radii for positive ions as given below: ( aligned Pr ³⁺ & =1.013 Å Sm ³⁺ & =0.964 Å Dy ³⁺ & =0.908 Å aligned ) Thus, statement (i) is not correct. (ii) Element Eu ((Z=63) ) can exist in ((+) 2 ) and ((+) 3 ) oxidation state. ( (+) ) 3oxidation state is the most common oxidation state for lanthanoid