Which set is expected to show the smallest difference in `IE_(1)` ?

Options

A. `He,Ne,Ar`
B. `B,N,O`
C. `Mg,Mg^(o+),Mg^(+2)`
D. `Fe,CO,Ni`

Answer

D

Explanation

Fe, Co and Ni are transition metal atoms and variation in properties of such elements (d-block elements) is quite less (as d `e^(-') s` are effectively shielded by the inner `e^(-')s)` .