Question

Effective nuclear charge of 3d electrons in zinc is?
A) $8.85$
B) $6.25$
C) $4.85$
D) $12.25$

Answer 1

We need to know that the decrease in effective nuclear charge by an electron due to the inner electrons, since they reduce its effect is known as the shielding effect. However, the screening effect is of the electron itself. It is the decrease in nuclear pull which is felt by the electron as the size keeps increasing.

Complete answer:
Now we can find the value of “effective nuclear charge” on the 3d electron of zinc.
From the question, we know that
Effective nuclear charge: $Z^* = Z - \sigma$
Z=atomic number
Zinc atomic number $\left( {Zn} \right) = 30$
$\sigma$= Shielding constant
Electronic configuration= $1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^{10}}$
For 3d electrons,
$\sigma = (0.35 \times 9) + (1 \times 18)$
On simplification we get,
$\sigma = 21.15$
$Z^* = Z - \sigma$
Now we can substitute the known values we get,
$= 30 - 21.15$
On simplification we get,
$= 8.85$
Therefore, Effective nuclear charge on 3d electron of Zinc is $8.85$
The 4s orbitals have a lower energy than the 3d, and so the 4s orbitals are filled first. We know that the 4s electrons are lost first during ionization. The electrons lost first will come from the highest energy level, furthest from the influence of the nucleus. Poor shielding means poor screening of nuclear charge. In other words, the nuclear charge is not effectively screened by electrons in question. The shielding effect of different orbitals is as follows:​ s orbital > p orbital> d orbital> f orbital.

Note:
As we move down the group the electrons are added to a new orbital which increases the atomic size of the atom, and reduces the influence of the nucleus on the outermost electron. For the same main energy level screening effect constant for s- orbital is the least and for d- orbital it is the highest.