To identify the strong reducing agent, we examine the definition of reducing agents. A reducing agent donates electrons to another substance, undergoing oxidation itself. Its effectiveness correlates with its electron-donating propensity.
Analysis of each ion:
Based on this analysis, \(\text{Eu}^{2+}\) is identified as the strong reducing agent due to its inclination to donate an electron and attain the stable +3 oxidation state.
Therefore, the correct answer is \(\text{Eu}^{2+}\).
Sc Ti V Cr Mn Fe Co Ni Cu Zn
Y Zr Nb Mo Tc Ru Rh Pd Ag Cd
La Hf Ta W Re Os Ir Pt Au Hg
In any transition series, as we move from left to right the d-orbitals are progressively filled and their properties vary accordingly.
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
The above are the two series of f-block elements in which the chemical properties won’t change much. The 5f-series elements are radioactive in nature and mostly are artificially synthesized in laboratories and thus much is not known about their chemical properties.