Answer: Option (D) is the correct answer.
Explanation:
Shielding effect is the effect in which nucleus of an atom is surrounded by number of electrons in such a manner that there will be decrease in attraction between nucleus and valence electrons.
So, more is the number of shells present in an atom more will be its shielding effect. Whereas smaller is the size of atom more will be attraction between its nucleus and valence electrons. So, it would be difficult to remove an electron from the valence shell.
For example, rubidium is larger in size so it has more number of shells and thus more shielding effect.
Thus, we can conclude that out of the given options rubidium would exhibit the greatest shielding effect.
