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Aufbau and Hund’s Rule Class 11 Chemistry MCQs with Answers
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Introduction Paragraph
Prepare for your CBSE Class 11 Chemistry board exams with this focused online practice test on “Aufbau and Hund’s Rule”, a key concept from Chapter 2: Structure of Atom (Part A: Physical Chemistry). These MCQs are designed strictly as per the NCERT syllabus, making them perfect for quick revision and concept reinforcement.
The Aufbau Principle explains the order in which electrons occupy atomic orbitals based on increasing energy levels, while Hund’s Rule describes how electrons fill degenerate orbitals singly with parallel spins before pairing up. Together, these rules form the foundation for understanding electronic configurations and atomic stability.
This quiz includes 30 NCERT-standard multiple-choice questions with instant feedback and explanations, ensuring that you grasp the logic behind each concept. Attempting this practice test will help students strengthen their understanding of electron arrangement, orbital order, and magnetic properties—crucial topics for both CBSE board exams and entrance tests like NEET and JEE (Main).
Sample MCQs (with Answers and Explanations)
Q1. The Aufbau principle states that electrons fill orbitals in order of:
A) Increasing atomic number B) Decreasing energy C) Increasing energy D) Random order
Answer: C) Increasing energy
Explanation: According to the Aufbau principle, electrons fill orbitals starting from the lowest to the highest energy levels.
Q2. Hund’s Rule is applied to:
A) Different energy levels B) Degenerate orbitals C) Non-degenerate orbitals D) Nucleus
Answer: B) Degenerate orbitals
Explanation: Hund’s Rule states that electrons occupy all degenerate orbitals singly with parallel spins before pairing occurs.
Q3. Which of the following configurations violates Hund’s Rule?
A) 1s² 2s² 2p³ B) 1s² 2s² 2p⁴ C) 1s² 2s² 2p² D) 1s² 2s² 2p⁵
Answer: C) 1s² 2s² 2p²
Explanation: In 2p², both electrons should occupy separate orbitals with parallel spins, not pair in one orbital.
Q4. The correct electron configuration of nitrogen (Z = 7) following Hund’s Rule is:
A) 1s² 2s² 2p³ B) 1s² 2s² 2p⁴ C) 1s² 2s² 2p² D) 1s² 2s¹ 2p⁵
Answer: A) 1s² 2s² 2p³
Explanation: Nitrogen has three unpaired electrons in 2p orbitals with parallel spins, following Hund’s Rule.
Q5. Which element shows an exception to the Aufbau Principle?
A) Copper B) Neon C) Magnesium D) Argon
Answer: A) Copper
Explanation: Copper has the configuration [Ar] 4s¹ 3d¹⁰ instead of [Ar] 4s² 3d⁹ due to extra stability of filled d-orbitals.