Practice tests · NEET

NEET d- and f-Block Elements: 5 practice MCQs with answers

By the PrepMatic team · Updated 9 Oct 2026 · 3 min read

The d- and f-block chapter covers the transition metals and the inner transition series. It is a Class 12 inorganic chapter with a mix of trends, small calculations and reactions. The five MCQs below test the usual oxidation state of lanthanoids, a spin-only magnetic moment, the behaviour of KMnO₄ in acid, lanthanoid contraction and coloured versus colourless ions.

What this chapter covers in the NEET syllabus

The NMC unit is d- and f-Block Elements, taught as a Class 12 NCERT chapter. The topics are:

• Position in the periodic table, electronic configurations and general characteristics of transition elements.
• Trends in the first transition series: atomic radii, ionisation enthalpy, oxidation states, colour, magnetic properties, catalytic behaviour, complex formation, interstitial compounds and alloys.
• Preparation, properties and uses of potassium dichromate and potassium permanganate.
• Lanthanoids: electronic configuration, oxidation states and lanthanoid contraction.
• Actinoids: electronic configuration and oxidation states.

Five practice MCQs on the d- and f-Block

Question 1

The most common oxidation state of the lanthanoids is:

• A. +2
• B. +3
• C. +4
• D. +1

Question 2

The spin-only magnetic moment of the Mn²⁺ ion (Z = 25) in BM is approximately:

• A. 1.73
• B. 3.87
• C. 4.90
• D. 5.92

Question 3

When acidified KMnO₄ oxidises Fe²⁺ to Fe³⁺, the manganese-containing product is:

• A. MnO₂
• B. MnO₄²⁻
• C. Mn²⁺
• D. Mn₂O₃

Question 4

Because of the lanthanoid contraction, which pair of elements has almost identical atomic radii?

• A. Ti and Zr
• B. Zr and Hf
• C. Cr and Mo
• D. Sc and Y

Question 5

Which of the following aqueous ions is colourless?

• A. Cu²⁺
• B. Fe³⁺
• C. Ni²⁺
• D. Zn²⁺

Answers and explanations

1. B. The characteristic and most stable oxidation state of the lanthanoids is +3. A few, such as cerium (+4) and europium (+2), also show other states, but +3 is common to all.
2. D. Mn²⁺ is 3d⁵ with five unpaired electrons. The spin-only formula μ = √[n(n + 2)] BM gives √(5 × 7) = √35 = 5.92 BM. The values 1.73, 3.87 and 4.90 correspond to one, three and four unpaired electrons.
3. C. In acidic solution MnO₄⁻ is reduced to Mn²⁺: MnO₄⁻ + 8H⁺ + 5Fe²⁺ → Mn²⁺ + 5Fe³⁺ + 4H₂O. The purple colour fades to near colourless, which is why KMnO₄ acts as its own indicator in titrations.
4. B. The 4f electrons shield poorly, so the lanthanoid series shrinks in size. As a result the atomic radii of the 4d and 5d elements of the same group become nearly equal. Zirconium (160 pm) and hafnium (159 pm) are the standard example, which is why their chemistry is so similar.
5. D. Colour in transition metal ions arises from d-d transitions, which need a partly filled d subshell. Zn²⁺ is 3d¹⁰ and has no space for such a transition, so it is colourless. Cu²⁺, Fe³⁺ and Ni²⁺ are coloured.

How to prepare the d- and f-Block

• Know the first-row configurations and the two exceptions (Cr and Cu). From these, you can count unpaired electrons for any ion, which gives magnetic moment, colour and the number of oxidation states.
• Use the spin-only formula quickly. Memorise the values for n = 1 to 5: 1.73, 2.83, 3.87, 4.90 and 5.92 BM. You will meet them in the coordination chapter too.
• Learn oxidation state patterns. Manganese shows the widest range (+2 to +7) in the first series. The highest oxidation states are shown in oxides and fluorides, and the stability of +2 increases across the series.
• Focus on the two compounds. For K₂Cr₂O₇ and KMnO₄, know their preparation steps, colours, the dichromate-chromate change with pH and the reduction products in acidic, neutral and basic media.
• Understand the lanthanoid contraction and its consequences, including the similar radii of Zr and Hf, the basic character trend of lanthanoid hydroxides, and why actinoids show more oxidation states than lanthanoids.

Revise this chapter in tables: one for configurations and properties, one for the two compounds, one for the f-block. For a view of the whole subject see the NEET Chemistry preparation guide, and for units see the NEET syllabus.

Take a full d- and f-Block test on PrepMatic

Check the tables you built with a topic test on PrepMatic: about 15 questions in 30 minutes, scored with NEET's negative marking. The free Basic plan includes topic tests, and you can keep going with Coordination Compounds or the practice hub.

← All practice tests