Question

The screening effect of d electrons is
A. much less than s-electrons
B. much more than s-electrons
C. equal to s-electrons
D. less than p-electrons

Answer 1

Hint: Screening effect is also known by the name shielding effect which can be explained as that phenomenon which occurs when the nucleus reduces the force of attraction on the valence electrons provided due to the presence of electrons in the inner shell.

Complete answer:
In a multi electron atom the electrons of the valence shell are attracted towards the nucleus and these electrons are also repelled by the electrons present in the inner shells. Because of this the actual force of attraction between the nucleus and the valence electrons is little bit decreased by these repulsive forces which act in the opposite directions.
This decrease in the force of attraction which was exerted by the nucleus on the valence electrons due to the presence of electrons in the inner shells is called screening effect or shielding effect.
The screening effect of d-electrons is less than that of p-electrons. We know that d and f electrons have a poor shielding effect as compared to s and p electrons. This is due to the reason that s and p electrons are close to the nucleus whereas d and f electrons are more away from the nucleus.

Thus we can say that option D is the correct answer.

Note:
The magnitude of the screening effect generally depends upon the number of inner electrons. Greater the number of inner electrons greater will be the value of the screening effect. The screening effect constant is represented by the symbol $\sigma $.