The reducing effect of the nuclear charge by the inner electrons for on outer electron is termed aas shielding (or screening). As a result of shielding, the outer electrons in an atom always experience less nnuclear charge than the actual nuclear charge Z. The effective nuclear charge `(Z^(**))` as experienced by an electron is then obtained by subtracting the total shielding contributions from alll the other electrons (i.e., except the one under consideration) from the actual nuclear charge.
`Z^(**)=Z-sigma`
Where `sigma`=sum of the shielding contributions. The rules for estimating contributions to `sigma` are as follows (Slater's rule) Contribution to shielding by each electron is :
`|{:("Electron","All Higher","Same","Group","Group"le),("Grpoup","Group","Group",n-1,n-2),(1s," "0,0.30,-,-),((ns,sp)," "0,0.35,0.85,1.00),((nd)or(nf)," "0,0.35,1.00,1.00):}|`
According to Slater's treatment, the energy of an electron in nth shell of an atom having atomic number Z is given by the empirical equation
`E=-13.6((Z^(**))/(n))^(2)eV`
`Z^(**)` = effective nuclear charge
Which one among the following sets of ions represents the collection of isoelectronic species?

Options

A. `S^(2-),CI^(-),K^(+),Ca^(2+),Sc^(3+)`
B. `N^(3-),O^(2-),Na^(+),Mg^(2+),AI^(3+)`
C. `K^(+),CI^(-),Mg^(2+),AI^(3+),Sc^(3+)`
D. (a) and (b) both

Answer

D