Question

The effective nuclear charge (\( Z_{\text{eff}} \)) experienced by 4s electrons of Cu(29) is:

• A. 3.70
• B. 2.70
• C. 1.70
• D. 0.70

Hint:

Effective nuclear charge increases across a period due to the increasing number of protons, but the shielding effect also increases with more electrons.

Answer 1

The Correct Option is A

Step 1: Understanding Effective Nuclear Charge.
The effective nuclear charge (\( Z_{\text{eff}} \)) is the net charge experienced by an electron in a multi-electron atom. It is calculated using the formula: \[ Z_{\text{eff}} = Z - S \] where \( Z \) is the atomic number and \( S \) is the shielding constant, which represents the effect of other electrons in the atom in shielding the nucleus.

Step 2: Calculation for Copper (Cu).
For copper (\( Z = 29 \)), the 4s electron is shielded by the inner electrons, especially the 1s, 2s, and 2p electrons. The shielding constant for the 4s electron can be estimated using Slater's rules or experimental values. For copper, the shielding constant \( S \) is approximately 1.30. Therefore, the effective nuclear charge is: \[ Z_{\text{eff}} = 29 - 1.30 = 3.70 \]

Step 3: Conclusion.
Thus, the effective nuclear charge experienced by the 4s electron of Cu is \( 3.70 \), which corresponds to option (1).