NEET (UG)

Practice Test 1 — The d- and f-Block Elements

12 questions • 18 minutes • auto-graded with full solutions

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Section A — MCQ (Single Correct & Statement-based)

Question 1

The electronic configuration of $\text{Cu}$ (Z = 29) is:

Solution: Fully-filled $d$ stability: $3d^{10} 4s^1$.

Question 2

Which ion has the highest spin-only magnetic moment?

Solution: $d^5$ has 5 unpaired electrons — the maximum.

Question 3

The colour of transition metal ions is due to:

Solution: Partly filled $d$ enables $d$–$d$ transitions.

Question 4

Statements: (I) Mn shows oxidation states from $+2$ to $+7$. (II) $\text{Sc}^{3+}$ is coloured. Which is/are correct?

Solution: I is correct; $\text{Sc}^{3+}$ ($d^0$) is colourless, so II is wrong.

Question 5

The lanthanoid contraction is caused by poor shielding by:

Solution: Diffuse $4f$ electrons shield poorly.

Question 6

Which pair has almost identical atomic sizes due to lanthanoid contraction?

Solution: Zr and Hf are nearly the same size.

Question 7

Actinoids differ from lanthanoids in being:

Solution: All actinoids are radioactive.

Question 8

$\text{KMnO}_4$ and $\text{K}_2\text{Cr}_2\text{O}_7$ are important as:

Solution: Both are strong oxidising agents.

Section B — Assertion & Reason

Question 9

A: Transition metals show variable oxidation states.
R: The energies of the $(n-1)d$ and $ns$ orbitals are close, so electrons from both can participate in bonding.

Solution: Similar orbital energies allow several oxidation states — R explains A.

Question 10

A: $\text{Zn}^{2+}$ salts are colourless.
R: $\text{Zn}^{2+}$ has a completely filled $3d^{10}$ configuration, so no $d$–$d$ transition is possible.

Solution: No $d$–$d$ transition means no colour — R explains A.

Question 11

A: Lanthanoids and actinoids have exactly the same number of oxidation states.
R: The $5f$ electrons of actinoids are more available for bonding than the $4f$ electrons of lanthanoids.

Solution: Actinoids show a wider range of states, so A is false; R correctly states why $5f$ are more available.

Question 12

A: Zirconium and hafnium are difficult to separate.
R: The lanthanoid contraction makes their atomic sizes almost identical.

Solution: Nearly identical sizes give very similar properties — R explains A.