NCERT  ·  Science  ·  Class IX  ·  Ch.4

Structure of the Atom
MCQ Master Series

Subatomic Particles · Bohr's Model · Shells · Valency · Isotopes · Isobars

🎯 50 Questions
⏱ 28 min Suggested
📊 3 Difficulty Tiers
🗂 5 Topics
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Question Intelligence

Quiz Analytics

A data-driven breakdown of all 50 questions by difficulty, exam origin and topic distribution.

📈 Distribution Overview

50
Total Questions
CBSE Board
26
State Board
15
Olympiad Level
9

🗂 Topic Coverage

Subatomic Particles
18%
Thomson's & Rutherford's Models
18%
Bohr's Atomic Model
20%
Electronic Configuration
24%
Isotopes & Isobars
20%
26
CBSE Board
15
State Board
9
Olympiad Level
Conceptual Framework

Key Concept Highlights

6 foundational pillars that power every question in this quiz. Understand these, and the answers follow naturally.

⚛️
Subatomic Particles
Proton (positive, in nucleus), Neutron (neutral, in nucleus), Electron (negative, in shells). Mass number A = P + N. Atomic number Z = number of protons = number of electrons (neutral atom).
🍑
Thomson's Model
"Plum pudding" model: positive sphere with electrons embedded uniformly. Failed to explain Rutherford's gold foil experiment.
🎯
Rutherford's Model
Gold foil experiment: most α-particles passed through → atom is mostly empty space. Few deflected/bounced back → dense, positive nucleus. Limitation: couldn't explain electron stability.
🪐
Bohr's Model
Electrons revolve in fixed orbits (energy levels) without radiating energy. Energy is absorbed/emitted only when electrons jump between orbits. Explains hydrogen spectrum.
🔢
Electronic Configuration
Shell capacity: K=2, L=8, M=18 (or 8 for Class IX). Fill shells from inside out. Valence electrons = electrons in outermost shell. Determines chemical behaviour.
🔄
Isotopes & Isobars
Isotopes: same atomic number (Z), different mass number (A). Eg: ¹H, ²H, ³H. Isobars: same mass number (A), different atomic number (Z). Eg: ⁴⁰Ar and ⁴⁰Ca.
Pedagogical Value

Why MCQs Matter

Multiple-choice questions are not mere guessing games — they are the sharpest diagnostic tool available to a competitive exam aspirant.

~10%

of CBSE Class IX Science — atomic models and electronic configuration are core

Quick Reference

Important Formula Capsules

4 must-memorise equations that surface repeatedly across CBSE and JEE papers.

Mass Number
\[ A = Z + N \quad (P + N) \]
Neutrons
\[ N = A - Z \]
Shell Capacity
\[ 2n^2 \quad (n = \text{shell number}) \]
Valence Electrons
\[ \text{Outermost shell electrons} \]
Learning Outcomes

What You Will Learn

By completing this quiz set you will have exercised all the following competencies.

01 Find the number of protons, neutrons, and electrons from atomic and mass numbers
02 Draw the atomic model of elements up to atomic number 20
03 Write the electronic configuration of the first 20 elements
04 Explain the limitations of Thomson's and Rutherford's models
05 State Bohr's postulates and explain why they improved on Rutherford's model
06 Distinguish between isotopes and isobars with two examples each
Exam Preparation

Strategy & Preparation Tips

4 evidence-based strategies to maximise your score in CBSE Boards and JEE.

Step 01
Configuration Cards for Z=1 to 20
Write the electronic configuration of all 20 elements on index cards. CBSE directly asks to "write the configuration of chlorine (Z=17)" — zero room for error.
Step 02
Mass Number vs Atomic Number
Biggest exam mistake: confusing A and Z. Drill this: Z = protons (never changes per element), A = protons + neutrons (can vary → isotopes).
Step 03
Model Timeline
Thomson (1897) → Rutherford (1911) → Bohr (1913). Each model fixed the previous one's flaw. CBSE asks "what limitation did Bohr's model overcome?"
Step 04
Isotope Uses
¹⁴C (carbon dating), ²³⁵U (nuclear fuel), ¹³¹I (thyroid cancer treatment), ²³Na (circulatory tracing). Four isotopes + uses = 4 direct MCQs.

Ready to Test Your Mastery?

50 questions  ·  Elapsed timer  ·  Instant scored results

⚡ Begin Structure of the Atom Quiz
🎯 Knowledge Check

Science — Structure Of The Atom

50 Questions Class 9 MCQs
1
Who discovered the electron?
2
What is the charge of an electron?
3
Who discovered the proton?
4
Who discovered the neutron?
5
The mass of an electron is approximately:
6
What is the charge on a proton?
7
The nucleus of an atom contains:
8
The atomic number is equal to the number of:
9
The mass number of an atom is:
10
Isotopes are atoms of the same element having:
11
Which of the following is an isotope of hydrogen?
12
Who proposed the planetary model of the atom?
13
The nucleus was discovered by:
14
In Rutherford’s model, most alpha particles passed straight through the foil because:
15
Bohr’s model explains:
16
The lowest energy level of an atom is called:
17
Which of the following represents an isotope pair?
18
The electronic configuration of oxygen (atomic number 8) is:
19
Maximum electrons in a shell are given by:
20
The valence shell of sodium has:
21
Isobars are atoms with:
22
Example of isobars:
23
The K-shell can have a maximum of:
24
The L-shell can have a maximum of:
25
What is the atomic number of carbon?
26
The neutral atom of an element has:
27
What particle decides the charge of the atom?
28
The isotope of chlorine are in ratio 3:1, their mass numbers are:
29
The average atomic mass of chlorine is:
30
Who proposed the modern atomic model?
31
The path of electron around nucleus is called:
32
The subatomic particles present inside the nucleus are:
33
The mass of proton is approximately:
34
The nucleus is:
35
The number of neutrons in \(^{14}_6C\) is:
36
The first orbit can hold:
37
The second orbit can hold:
38
Which particle is neutral?
39
Which of the following is not an isotope of hydrogen?
40
The number of electrons in \(\mathrm{Mg^{2+}}\) (Z=12) is:
41
The charge on an alpha particle is:
42
Who proposed that electrons revolve in fixed orbits without radiating energy?
43
The valence electrons determine:
44
The formula to calculate number of neutrons is:
45
Which shell has the highest energy?
46
An atom of sodium has electronic configuration 2,8,1. It belongs to which period?
47
Electrons are arranged around nucleus according to:
48
The number of shells in chlorine (Z=17) atom is:
49
What is the valency of oxygen?
50
Which of the following is the correct electronic configuration of calcium (Z=20)?
📚
ACADEMIA AETERNUM तमसो मा ज्योतिर्गमय · Est. 2025
Sharing this chapter
Structure Of The Atom | Science Class 9 | Academia Aeternum
Structure Of The Atom | Science Class 9 | Academia Aeternum — Complete Notes & Solutions · academia-aeternum.com
The chapter “Structure of the Atom” introduces the fascinating world of subatomic particles — electrons, protons, and neutrons — and the models proposed by scientists like J.J. Thomson, Rutherford, and Niels Bohr. These 50 multiple choice questions (MCQs) are designed according to the latest NCERT Class 9 Science syllabus, covering key concepts like atomic models, isotopes, isobars, electronic configuration, valency, and more. Each question includes a correct answer and a concise explanation…
🎓 Class 9 📐 Science 📖 NCERT ✅ Free Access 🏆 CBSE · JEE
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Exam tip: Sharing chapter notes with your study group creates a reinforcement loop. Teaching a concept is the fastest path to mastering it.

Frequently Asked Questions

Atoms have a nucleus made of protons and neutrons, with electrons arranged in shells around it.

James Chadwick discovered the neutron in 1932.

Protons, neutrons, and electrons.

The number of protons in the nucleus of an atom.

The sum of protons and neutrons in the atom’s nucleus.

Atoms of the same element with different numbers of neutrons.

Atoms of different elements with the same mass number but different atomic numbers.

The number of electrons an atom can gain, lose, or share to become stable.

Electrons revolve in fixed orbits (shells) around the nucleus without losing energy.

Atomic number is protons; mass number is protons + neutrons.

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    Structure of the Atom — Learning Resources

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    ACADEMIA AETERNUM तमसो मा ज्योतिर्गमय · Est. 2025
    Sharing this chapter
    Structure Of The Atom | Science Class 9 | Academia Aeternum
    Structure Of The Atom | Science Class 9 | Academia Aeternum — Complete Notes & Solutions · academia-aeternum.com
    The chapter “Structure of the Atom” introduces the fascinating world of subatomic particles — electrons, protons, and neutrons — and the models proposed by scientists like J.J. Thomson, Rutherford, and Niels Bohr. These 50 multiple choice questions (MCQs) are designed according to the latest NCERT Class 9 Science syllabus, covering key concepts like atomic models, isotopes, isobars, electronic configuration, valency, and more. Each question includes a correct answer and a concise explanation…
    🎓 Class 9 📐 Science 📖 NCERT ✅ Free Access 🏆 CBSE · JEE
    Share on
    WhatsApp
    Telegram
    X / Twitter
    Facebook
    Instagram
    Threads
    Pinterest
    LinkedIn
    Quora
    Discord
    Reddit
    Email
    academia-aeternum.com/class-9/science/structure-of-the-atom/mcqs/ Copy link
    💡
    Exam tip: Sharing chapter notes with your study group creates a reinforcement loop. Teaching a concept is the fastest path to mastering it.

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