chemistry 2nd year 2nd chapter kpk book #expected mcqs 2nd year board and MDCAT NUMS MCQS

*Correct answer: D. Cu⁺*

*Why the others are wrong*:

- *Ni²⁺*: Electronic config is $[\text{Ar}] 3d^8$. Has 2 unpaired electrons → paramagnetic
- *Cr³⁺*: Electronic config is $[\text{Ar}] 3d^3$. Has 3 unpaired electrons → paramagnetic
- *Mn²⁺*: Electronic config is $[\text{Ar}] 3d^5$. Has 5 unpaired electrons → paramagnetic
- *Cu⁺*: Electronic config is $[\text{Ar}] 3d^{10}$. All electrons are paired → diamagnetic

*Key rule for MDCAT/NUMS*:
Diamagnetic = all electrons paired → Net magnetic moment = 0 → weakly repelled by magnetic field
Paramagnetic = has unpaired electrons → attracted to magnetic field

The diagram on the right actually shows it: Cu⁺ is diamagnetic, Mn²⁺ is paramagnetic.

So the checkmarks in the image for A, B, C are mistakes. For 2nd Year Board 2026, remember: Cu⁺ and Zn²⁺ are common diamagnetic ions because they have full $d^{10}$ subshells.

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