Q.55 Chemistry · Section A ⭐ 360° Option Elimination Active

NEET 2024 Chemistry Question 55 Solution

Topic: Structure of Atom · Official NTA Booklet Code T1

Question

Match List I (Quantum Number) with List II (Information provided). List I: A. mₗ; B. mₛ; C. l; D. n. List II: I. shape of orbital; II. size of orbital; III. orientation of orbital; IV. orientation of spin of electron. Choose the correct answer from the options given below:

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Verified Against NTA Final Answer Key

Option (4) : A-III, B-IV, C-I, D-II

📚 Structure of Atom Easy

📋 Given Parameters & Problem Setup

Quantum Number A m_l (magnetic quantum number)

Quantum Number B m_s (spin quantum number)

Quantum Number C l (azimuthal / orbital angular momentum quantum number)

Quantum Number D n (principal quantum number)

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The 30-Second Exam Hall Shortcut: ⚡ Quantum Number Direct Definition Flashcard

⏱️ Save ~30 seconds

n = Size & energy (II); l = Shape of subshell (I); m_l = Spatial orientation of orbital (III); m_s = Electron spin direction (IV)!

1 Principal quantum number n determines shell size and primary energy level -> D-II.

2 Azimuthal quantum number l determines orbital angular momentum and three-dimensional shape (s=sphere, p=dumbbell, d=cloverleaf) -> C-I.

3 Magnetic quantum number m_l determines spatial orientation of the orbital in space relative to coordinate axes -> A-III.

4 Spin quantum number m_s determines the orientation of intrinsic electron spin (+1/2 or -1/2) -> B-IV.

5 Perfect match: A-III, B-IV, C-I, D-II -> Option (4) in 5 seconds!

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Why You Can 100% Trust This Shortcut: NCERT Chemistry · Structure of Atom (Quantum numbers and their physical significance).

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Principal Quantum Number (n)

The principal quantum number n can be any positive integer (1, 2, 3, ...). It identifies the principal electron shell, governs the effective size of the electron cloud (radius r ∝ n²/Z), and predominantly determines the orbital energy:

n \in \{1, 2, 3, \dots\} \implies \text{Determines Size and Energy of Orbital}

Step 2

Azimuthal / Orbital Angular Momentum Quantum Number (l)

For a given n, l takes integral values from 0 to (n - 1). It dictates the orbital angular momentum and defines the three-dimensional geometric shape of the orbital:

L = \sqrt{l(l + 1)}\hbar, \quad l = 0(s), 1(p), 2(d), 3(f) \implies \text{Determines Shape}

Step 3

Magnetic Quantum Number (m_l)

For a given l, m_l ranges from -l to +l through zero (total 2l + 1 values). It specifies the spatial orientation of the orbital with respect to an external magnetic field:

m_l \in \{-l, \dots, 0, \dots, +l\} \implies \text{Determines Spatial Orientation of Orbital}

Step 4

Electron Spin Quantum Number (m_s)

The electron spin quantum number accounts for the intrinsic angular momentum of the electron, with two allowable spin orientations: +1/2 (spin-up) and -1/2 (spin-down):

m_s = \pm \frac{1}{2} \implies \text{Determines Orientation of Spin of Electron}

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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 (1)

✗ Incorrect

Verdict & Scientific Reason:

Swaps the roles of l (shape) and n (size).

⚠️

Student Fallacy (Why candidates pick this trap): Confusing azimuthal quantum number with principal quantum number.

2 (2)

✗ Incorrect

Verdict & Scientific Reason:

Assigns size to magnetic quantum number.

⚠️

Student Fallacy (Why candidates pick this trap): Complete confusion of all quantum properties.

3 (3)

✗ Incorrect

Verdict & Scientific Reason:

Mismatches magnetic quantum number with shape.

⚠️

Student Fallacy (Why candidates pick this trap): Believing ml determines shape.

4 (4)

✓ 100% Correct

Verdict & Scientific Reason:

Unquestionable textbook alignment.

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Why this is airtight: None.

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NTA Trap Alert: Distinguishing Orbital Orientation (ml) from Spin Orientation (ms)

Both ml and ms use the word "orientation". ml is the orientation of the orbital in space, while ms is the orientation of the electron’s intrinsic spin axis.

🛡️ How to avoid the -1 mark: Check the object being oriented: orbital orientation = ml; electron spin orientation = ms.

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Core NEET Syllabus Standard

Chemistry Core Physical Chemistry · Structure of Atom Standard Benchmark

Core Scientific Principle Tested:

"The state of an electron in an atom is completely described by four quantum numbers: n (size/shell), l (shape/subshell), ml (spatial orientation), and ms (spin orientation)."

Syllabus Focus: Quantum Mechanical Model of the Atom: Quantum Numbers

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

n = Number (Size), l = Lines (Shape), ml = Magnetic alignment (Orientation), ms = Spin!

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Mathematical Relation Between Number of Magnetic Orbitals (n_m) and Azimuthal Quantum Number (l)

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NEET 2024 Chemistry Question 55 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Quantum Number Direct Definition Flashcard

Step-by-Step Rigorous Workflow & Mathematical Proof

Principal Quantum Number (n)

Azimuthal / Orbital Angular Momentum Quantum Number (l)

Magnetic Quantum Number (m_l)

Electron Spin Quantum Number (m_s)

360° Option Elimination Engine Key Feature

NTA Trap Alert: Distinguishing Orbital Orientation (ml) from Spin Orientation (ms)

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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