Question

Which among the following elements has completely filled 4d-orbital?

• A. Ag
• B. Cd
• C. Sc
• D. Zr

Hint:

The elements at the very end of the d-block groups (Group 12: Zn, Cd, Hg) always have completely filled $\text{d}^{10}$ configurations along with fully filled $\text{s}^2$ shells!

Answer 1

The Correct Option is B

Step 1: We want a full 4d shell.
A completely filled 4d means $4d^{10}$. So we check the four elements.

Step 2: Check the configurations.
Sc has no 4d electrons. Zr is $[Kr]4d^2 5s^2$, only partly filled. Ag is $[Kr]4d^{10}5s^1$. Cd is $[Kr]4d^{10}5s^2$.

Step 3: Pick the stable one.
Cadmium ends the 4d series with a filled 4d and a filled 5s, a neat closed shell. So it is the clear choice.
\[ \boxed{\text{Cd, option 2}} \]