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
Atomic radii of the noble gases are larger than the precedent elements of the same periods because:

Options

A. atomic radius of noble gas is expressed as van der Waals' radius
B. valence shell electrons are completely filled so there is interelectronic repulsions
C. both (a) and (b)
D. none of the above

Answer

C