Question

In Cu atom $Z_{eff}$ value for 3d & 4s electron are respectively}

• A. 7.85 each
• B. 3.70 each
• C. 7.85 and 3.70
• D. 3.70 and 7.85

Hint:

Concept Tip: Inner electrons experience larger effective nuclear charge than outer electrons because shielding is smaller near the nucleus.

Answer 1

The Correct Option is C

Concept:
Effective nuclear charge (\(Z_{eff}\)) is the net positive charge experienced by an electron after shielding effect.
Step 1:
Copper (\(Z=29\)) has configuration: \[ [Ar]~3d^{10}4s^{1} \]
Step 2:

• 3d electrons are closer to nucleus and experience higher attraction.
• 4s electron is farther away and more shielded.
Step 3:
Approximate values are: \[ Z_{eff}(3d)=7.85 \] \[ Z_{eff}(4s)=3.70 \]
Step 4:
Therefore: \[ \boxed{7.85 \text{ and } 3.70} \] \[ \boxed{\text{Correct Option = (3)}} \]