Question

Screening effect is not observed in:
A. \[H{e^ + }\]
B. \[L{i^{2 + }}\]
C. \[B{e^{3 + }}\]
D. all of the above

Answer 1

Hint: The screening effect is the phenomenon which occurs when the nucleus of the atom reduces its force of attraction on the electrons present in the valence shell because of the presence of electrons in the inner shell. It can be seen in atoms containing more electrons in the valence shell.

Complete step by step answer:
The screening effect is observed in the atoms which contain more than one valence electrons and more electron shells. The electrons present in the valence shell are attracted by the positively charged nucleus and repulsion is observed between the valence electrons and the electrons present in the inner shells. As a result, there is an decrease in force of attraction between the electrons present in the valence shell and the nucleus. This effect is known as the screening effect.
The atomic number of helium is 2. The electronic configuration of helium is \[1{s^2}\], by losing one electron it forms \[H{e^ + }\] and the resulting electronic configuration is \[1{s^1}\]. It contains one electron in the valence shell.
The atomic number of lithium is 3. The electronic configuration of lithium is \[1{s^2}2{s^1}\], by losing two electron it forms \[L{i^{2 + }}\] and the resulting electronic configuration is \[1{s^1}\]. It contains one electron in the valence shell.
The atomic number of beryllium is 4. The electronic configuration of lithium is \[1{s^2}2{s^2}\], by losing three electron it forms \[B{e^{3 + }}\] and the resulting electronic configuration is \[1{s^1}\]. It contains one electron in the valence shell.
As, all the ions contain only one electron in the valence shell. Thus all of them do not observe screening effects.

Therefore, the correct option is D.

Note: The screening effect is also known as shielding effect. The magnitude of the screening effect is dependent on the number of electrons present in the inner shells.