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Question: Screening effect is not observed in: A. \( H{e^ + } \) B. \( L{i^{2 + }} \) C. \( B{e^{3 + }...

Screening effect is not observed in:
A. He+H{e^ + }
B. Li2+L{i^{2 + }}
C. Be3+B{e^{3 + }}
D. In all the above cases

Explanation

Solution

Hint : There is a difference in the attraction forces between electrons and nucleus, this causes the reduction in the effective nuclear charge on the electron cloud. This effect is known as the screening effect. There must be more than one electron in the atom to show screening effect. It is mostly observed in elements having higher atomic numbers.

Complete Step By Step Answer:
Screening effect which is also known as shielding effect that refers to atomic shielding or electron shielding. This effect describes the difference between the attraction forces of electrons and nucleus in any atom having more than one electron. Mostly it is shown by the elements with higher atomic number.
From the given options:
In the case of helium, it has atomic number 22 . And the electronic configuration as;
He=1s2He = 1{s^2}
So, electronic configuration of He+H{e^ + } will be;
He+=1s1H{e^ + } = 1{s^1}
As it has only one electron in its shell so screening effect will not be observed in He+H{e^ + } .
In the case of lithium, it has atomic number 33 . And the electronic configuration as;
Li=1s22s1Li = 1{s^2}2{s^1}
So, the electronic configuration of Li2+L{i^{2 + }} will be;
Li2+=1s1L{i^{2 + }} = 1{s^1}
As it also has only one electron in its shell so screening effect will not be observed in Li2+L{i^{2 + }} .
In the case of beryllium, it has atomic number 44 . And the electronic configuration as;
Be=1s22s2Be = 1{s^2}2{s^2}
So, the electronic configuration of Be3+B{e^{3 + }} will be;
Be3+=1s1B{e^{3 + }} = 1{s^1}
As it also has only one electron in its shell so screening effect will not be observed in Be3+B{e^{3 + }} .
Hence, screening effect is not observed in all of them.
So, option D is correct.

Note :
There is a shielding effect that is observed between sublevels within the same principal energy level. An electron in the s−sublevelss - sublevels is capable of shielding electrons in the p−sublevelsp - sublevels of the same principal energy level. This is because of the spherical shape of the s−orbitals - orbital .