Question

Why screening effect remain constant on moving top to bottom in a group of periodic table?

Answer 1

I think it is not so. Because on moving from top to bottom one more outermost shell is added and screening effect increases. However on moving from 3d to 4d or 4d to 5d the effect is less pronounced due to lesser penetration power of d electrons. Further this effect decrease on moving from 4f to 5f because of lesser penetration power and diffuse nature of f electrons. So basically screening effect is less pronounced in lowermost rows. That is why lower elements show inert pair effect as d and f electrons are not fully able to screen the outer s electrons from nuclear charge.

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