Question

What is the screening constant for the outer electron of H?

Answer 1

According to the question, screening constantly measures the shielding of an electron from the charge of the nucleus by the inner electrons. It is denoted by $\left( \sigma \right)$. The magnitude of this effect depends on the number of electrons in the inner shell.
Formula used – $\sigma \text{=Z-}{{\text{Z}}^{*}}$
Where $\sigma$ is screening constant
Z is atomic number
${{\text{Z}}^{*}}$ is effective nuclear charge

Complete step by step answer:
In this question we have to find the screening constant so that we need to know the atomic number and effective nuclear charge of H i.e. hydrogen.
So for atomic numbers we have to write electronic configurations of hydrogen.
Electronic configuration of hydrogen is $1{{s}^{1}}$
So atomic number of hydrogen is 1
Now, the effective nuclear charge of hydrogen is 1 that can be taken from the periodic table.
Effective nuclear is 1
According to the formula now we have to substitute the values and then we have to find the value of the screening constant.
$\sigma \text{=Z-}{{\text{Z}}^{*}}$
$\sigma \text{=1-1}$
$\sigma \text{=0}$

So the value of the screening constant is zero.
Note:
There is another name of screening effect i.e. shielding effect. This phenomenon occurs when the nucleus reduces its force of attraction on the valence electrons due to the presence of electrons in the inner shell. Outer electrons experience attraction from the nucleus and repulsion from the inner electrons. As the attraction between the nucleus decreases, the repulsion increases between the inner electrons and outer electrons. The order of screening effect is s>p>d>f. As Electron will experience the greatest effective nuclear charge when in s-orbital, then a p-orbital and so on. Ionisation energy increases with an increase in penetration power.