Q.71 Chemistry ⭐ 360° Option Elimination Active

NEET 2025 Chemistry Question 71 Solution

Topic: The d- and f-Block Elements · Official NTA Booklet Code 45

Question

Given below are two statements: Statement I: Ferromagnetism is considered as an extreme form of paramagnetism. Statement II: The number of unpaired electrons in a Cr²⁺ ion (Z = 24) is the same as that of a Nd³⁺ ion (Z = 60). In the light of the above statements, choose the correct answer from the options given below:

✓

Verified Against NTA Final Answer Key

Option (3) : Statement I is true but Statement II is false

📚 The d- and f-Block Elements Medium

📋 Given Parameters & Problem Setup

Statement I Ferromagnetism is considered as an extreme form of paramagnetism.

Statement II The number of unpaired electrons in a Cr²⁺ ion (Z = 24) is the same as that of a Nd³⁺ ion (Z = 60).

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The 30-Second Exam Hall Shortcut: ⚡ NCERT Magnetism Text & Unpaired Electron Count

⏱️ Save ~40 seconds

Statement I is an NCERT verbatim quote: "Ferromagnetism is considered as an extreme form of paramagnetism" (TRUE)! Cr²⁺ (3d⁴) has 4 unpaired electrons. Nd³⁺ (4f³) has 3 unpaired electrons. 4 ≠ 3 ⟹ Statement II is FALSE!

1 Check Statement I: NCERT Chapter 8 Section 8.3.8 states verbatim: "Ferromagnetism is an extreme form of paramagnetism." In ferromagnetic materials, domains spontaneously align parallel, creating permanent magnetization. Statement I is TRUE.

2 Check Statement II: Chromium (Z = 24) has configuration [Ar] 3d⁵ 4s¹. Removing 2 electrons gives Cr²⁺: [Ar] 3d⁴ (n = 4 unpaired electrons).

3 Neodymium (Z = 60) is a lanthanoid with configuration [Xe] 4f⁴ 6s². Removing 3 electrons gives Nd³⁺: [Xe] 4f³ (n = 3 unpaired electrons).

4 Cr²⁺ has 4 unpaired electrons, while Nd³⁺ has 3 unpaired electrons. They are NOT the same! Statement II is FALSE.

5 Conclusion: Statement I is true but Statement II is false.

6 Select Option (3) in under 15 seconds!

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Why You Can 100% Trust This Shortcut: Oxidation States and Standard Electrode Potentials of 3d Metals (NCERT Chemistry · d- and f-Block Elements).

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Evaluate Statement I (Nature of Ferromagnetism)

Analyze the physical and chemical definition of ferromagnetism from the NCERT text:

\text{Ferromagnetism} = \text{Extreme form of paramagnetism with permanent domain alignment}

• Paramagnetic substances are weakly attracted by a magnetic field due to unpaired electrons.
• When exchange coupling forces magnetic dipoles of adjacent atoms to align spontaneously in large macroscopic domains, the substance exhibits ferromagnetism (e.g., Fe, Co, Ni).
• NCERT d- and f-Block Elements explicitly states: "Ferromagnetism is an extreme form of paramagnetism."
• Statement I is unequivocally TRUE.

Step 2

Calculate Unpaired Electrons in Cr²⁺ (Z = 24)

Write the electronic configuration of chromium and its divalent cation:

\text{Cr (Z = 24): } [\text{Ar}] 3d^5 4s^1 \xrightarrow{-2e^-} \text{Cr}^{2+}: [\text{Ar}] 3d^4

• According to Hund’s rule of maximum multiplicity, the 4 electrons occupy 4 degenerate d-orbitals singly.
• Number of unpaired electrons in Cr²⁺: n = 4.

Step 3

Calculate Unpaired Electrons in Nd³⁺ (Z = 60) and Compare

Write the electronic configuration of neodymium and its trivalent lanthanoid cation:

\text{Nd (Z = 60): } [\text{Xe}] 4f^4 6s^2 \xrightarrow{-3e^-} \text{Nd}^{3+}: [\text{Xe}] 4f^3

• The 3 electrons occupy 3 of the seven degenerate 4f-orbitals singly.
• Number of unpaired electrons in Nd³⁺: n = 3.
• Since 4 ≠ 3, Statement II is FALSE.
• Statement I is true but Statement II is false, matching Option (3).

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 A

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Statement II is false (Cr²⁺ has 4, Nd³⁺ has 3 unpaired electrons).

⚠️

Student Fallacy (Why candidates pick this trap): Miscounting f-electrons in Nd³⁺ as 4.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Statement I is true.

⚠️

Student Fallacy (Why candidates pick this trap): Doubting whether ferromagnetism is related to paramagnetism.

3 C

✓ 100% Correct

Verdict & Scientific Reason:

100% correct. Ferromagnetism is an extreme form of paramagnetism, and Cr²⁺ (4) ≠ Nd³⁺ (3).

💡

Why this is airtight: None; rigorous electronic configuration analysis.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Inverts truth values of both statements.

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Student Fallacy (Why candidates pick this trap): Multiple errors.

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NTA Trap Alert: Forgetting to Remove an Electron from 4f in Nd³⁺

Nd has 4f⁴ 6s². When forming the trivalent ion Nd³⁺, it loses TWO 6s electrons AND ONE 4f electron, leaving 4f³ (3 unpaired electrons)! Students who only remove the two 6s electrons mistakenly get 4f⁴ (4 unpaired electrons) and falsely mark Statement II as true!

🛡️ How to avoid the -1 mark: For M³⁺ lanthanoids, always remove two 6s electrons and one 4f electron: Nd³⁺ is 4f³!

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Core NEET Syllabus Standard

NEET Chemistry Core Syllabus · The d- and f-Block Elements Standard Benchmark

Core Scientific Principle Tested:

"Ferromagnetism is extreme paramagnetism; Cr²⁺ is 3d⁴ (4 unpaired e⁻); Nd³⁺ is 4f³ (3 unpaired e⁻)."

Syllabus Focus: Magnetic Properties & Lanthanoid Electronic Configurations

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

Cr²⁺ has 4 (3d⁴), Nd³⁺ has 3 (4f³) ⟹ Not equal! Statement I true, II false (Option 3)!

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NEET 2025 Chemistry Question 71 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ NCERT Magnetism Text & Unpaired Electron Count

Step-by-Step Rigorous Workflow & Mathematical Proof

Evaluate Statement I (Nature of Ferromagnetism)

Calculate Unpaired Electrons in Cr²⁺ (Z = 24)

Calculate Unpaired Electrons in Nd³⁺ (Z = 60) and Compare

360° Option Elimination Engine Key Feature

NTA Trap Alert: Forgetting to Remove an Electron from 4f in Nd³⁺

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

🔗 Related Questions — The d- and f-Block Elements

High Melting Points of 3d Transition Metals (Assertion-Reason)

Unpaired 4f Electrons in Trivalent Lanthanoid Cations

Thermal Decomposition of Potassium Permanganate

Spin-Only Magnetic Moments of 3d Transition Metal Ions

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