Home Chemistry Classification of Elements and Periodicity Shielding Effect & Zeff Screening effect is the effect produced by i…
Chemistry Classification of Elements and Periodicity Shielding Effect & Zeff Comprehension
Published on: August 12, 2026

Screening effect is the effect produced by intervening electrons between nucleus and valence electrons. They shield the nucleus from valence electron and effective nuclear charge decreases if there is less shielding effect, the effective nuclear charge decreases. Valence electrons are attracted by nucleus and repelled by other electrons.

Net attractive force on electron under consideration = Z – σ = (Nuclear charge – screening effect) which is Slater's formula for screening constant.

* If one electron is present in outermost orbit, there will be no screening in that orbital.

* Each electron contributes 0.35 (total electrons minus 1) present in outermost shell

* In penultimate energy level, electrons contribute 0.85.

* A contribution of 1.0 is from remaining electrons (present in last but one energy level)

(i)The effective nuclear charge for 4s electrons of Zn will be –

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CHECK THE SOLUTION.

(i)

Sol. For 4s – electron :

1 × 0.35 + 10 × 0.85 + 1.0 × 18 = 0.35 + 8.5 + 18.0 = 26.85

(ii)

Sol. There are six lobes in most of the f -orbitals

(iii)

Sol. Lesser the shielding effect, more will be force of attraction between valence electron and nucleus, smaller will be atomic size.

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