Question

Which of the following statements are true regarding variation of $Z_{eff}$ on valence shell electron for elements in the periodic table as per Slater's Rule.

• A. On moving along the period from left to right $Z_{eff}$ increases by 0.65 in s and p-block.
• B. On moving along the period from left to right in inner transition elements, $Z_{eff}$ remains constant.
• C. On moving along the period, from left to right in 3d series $Z_{eff}$ increases by 0.15 without any exception.
• D. Order of sheilding power of electron corresponds to ns > np > nd >nf.

Answer 1

Answer: (A), (B), (D)

The true statements are (A), (B) and (D).

Answer 2

Explanation of the Solution

• (A) In the s and p blocks, according to Slater's rules, when you add one proton across a period the additional same‐shell electron contributes 0.35 to shielding. Thus the net increase in Zeff is approximately 1 – 0.35 = 0.65.
• (B) In inner transition (lanthanide/actinide) series, the added f‐electrons shield very poorly, so the effective nuclear charge on the valence electrons remains nearly constant.
• (C) In the 3d series the increase in Zeff is not uniformly 0.15. The change depends on the shielding by added 3d electrons (each contributing ≈0.35) so the net increment is not a fixed 0.15.
• (D) Slater’s rules imply that electrons with lower angular momentum (ns) penetrate more (and shield more effectively) than np, which in turn shield better than nd and then nf; hence, the order is ns > np > nd > nf.