Question

With the increase in the atomic number, screening effect increases both in group and period.
State whether the given statement is true or false.
(A) True
(B) False

Answer 1

In order to tell whether the screening effect increases both in group and period, we must know what a screening effect is. Screening effect is the shield of the electron from the pull of the nucleus. Screening effect can also be referred to as the shielding effect.

Complete Solution :
- Let us first understand what a screening effect is. In the multielectron atom, the nucleus will attract the valence electron towards itself, these attractions are repelled by the electrons that are present in the inner shells. The force of attraction between the nucleus and the valence electron will be decreased by the repulsive force which are acting in the opposite direction. The decrease in the force of attraction between the nucleus and valence electrons is called the screening effect. The symbol for the screening effect is S.
- Down the group the number of inner shells increases, therefore, the shielding effect also increases in the group. But across the period the atomic number will increase and no change in the number of shells. Therefore, the screening effect will not increase across the period.
The given statement is false.
So, the correct answer is “Option B”.

Note: The shielding effect is helpful for determining the effective nuclear charge of an atom or molecule. In a multielectron atom, the net positive charge experienced by the atom is called effective nuclear charge. Effective nuclear charge is given by the following formula
${Z^ * } = Z - S$
Where S is the shielding constant, Z is the atomic number and ${Z^ * }$ is the effective nuclear charge.