SEBA Class 9 Science Chapter 4 Structure of the Atom MCQs (2026–27) – Assam Eduverse
The SEBA Class 9 Science Chapter 4 Structure of the Atom MCQs (2026–27) are prepared strictly according to the latest ASSEB syllabus and updated board examination pattern. These SEBA Class 9 Science Chapter 4 Structure of the Atom MCQs include conceptual objective questions, numerical-based MCQs, and board-oriented practice sets designed to strengthen exam preparation.
Prepared by subject experts of Assam Eduverse, these seba class 9 science chapter 4 mcqs focus on important concepts such as discovery of electrons, protons and neutrons, Thomson’s model, Rutherford’s model, Bohr’s model, atomic number, mass number, isotopes, and isobars. Practicing these structure of the atom mcqs class 9 seba and assam board class 9 science objective questions improves conceptual clarity and accuracy.
Regular revision of these ASSEB Class 9 Science Important MCQs ensures strong preparation for the 2026–27 board examination and enhances scoring potential in MCQ-based assessments.
SEBA Class 9 Science Chapter 4 Structure of the Atom MCQs – ASSEB 2026–27 Board Exam Practice
Table of Contents
Q1. Canal rays are positively charged radiations discovered by:
(a) J.J. Thomson
(b) E. Goldstein
(c) Rutherford
(d) Chadwick
Answer: (b) E. Goldstein
Q2. The charge on a proton is:
(a) –1
(b) +1
(c) 0
(d) +2
Answer: (b) +1
Q3. The mass of a proton is approximately:
(a) Equal to electron
(b) Negligible
(c) One unit
(d) Half unit
Answer: (c) One unit
Q4. Thomson proposed that electrons are embedded in a:
(a) Negatively charged sphere
(b) Neutral sphere
(c) Positively charged sphere
(d) Hollow space
Answer: (c) Positively charged sphere
Q5. According to Thomson’s model, an atom is electrically neutral because:
(a) It has no charge
(b) Positive and negative charges are equal
(c) It contains neutrons
(d) Electrons have no mass
Answer: (b) Positive and negative charges are equal
Q6. Rutherford used which metal foil in his experiment?
(a) Silver
(b) Platinum
(c) Gold
(d) Copper
Answer: (c) Gold
Q7. Most alpha particles passed through the gold foil because:
(a) The foil was thick
(b) Atom is mostly empty space
(c) Alpha particles are light
(d) Nucleus is large
Answer: (b) Atom is mostly empty space
Q8. The positively charged center of an atom is called:
(a) Electron
(b) Proton
(c) Nucleus
(d) Shell
Answer: (c) Nucleus
Q9. The size of nucleus compared to atom is:
(a) Larger
(b) Equal
(c) Very small
(d) Half
Answer: (c) Very small
Q10. Who discovered neutron?
(a) Rutherford
(b) J.J. Thomson
(c) Chadwick
(d) Goldstein
Answer: (c) Chadwick
Q11. The maximum number of electrons in K-shell is:
(a) 8
(b) 2
(c) 18
(d) 32
Answer: (b) 2
Q12. The maximum number of electrons in L-shell is:
(a) 2
(b) 4
(c) 8
(d) 18
Answer: (c) 8
Q13. The formula to calculate maximum number of electrons in a shell is:
(a) n²
(b) 2n
(c) 2n²
(d) n³
Answer: (c) 2n²
Q14. The outermost shell of an atom can have maximum:
(a) 2 electrons
(b) 4 electrons
(c) 6 electrons
(d) 8 electrons
Answer: (d) 8 electrons
Q15. Valency of an atom depends on:
(a) Total electrons
(b) Neutrons
(c) Electrons in outermost shell
(d) Atomic mass
Answer: (c) Electrons in outermost shell
Q16. Atomic number is equal to number of:
(a) Neutrons
(b) Electrons
(c) Protons
(d) Nucleons
Answer: (c) Protons
Q17. Mass number is equal to:
(a) Protons + electrons
(b) Protons + neutrons
(c) Neutrons only
(d) Electrons only
Answer: (b) Protons + neutrons
Q18. Isotopes have same:
(a) Mass number
(b) Atomic number
(c) Neutrons
(d) Physical properties
Answer: (b) Atomic number
Q19. Isobars have same:
(a) Atomic number
(b) Protons
(c) Mass number
(d) Electrons
Answer: (c) Mass number
Q20. Valency of oxygen (atomic number 8) is:
(a) 1
(b) 2
(c) 6
(d) 8
Answer: (b) 2
Q21. Assertion (A): Most of the space in an atom is empty.
Reason (R): Most alpha particles passed through the gold foil without deflection.
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true but R is not correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: (a) Both A and R are true and R is correct explanation of A
Q22. Assertion (A): Neutrons have no charge.
Reason (R): Neutrons are present in the nucleus of atom.
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true but R is not correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: (b) Both A and R are true but R is not correct explanation of A
Q23. Assertion (A): Atomic number determines the identity of an element.
Reason (R): Atomic number is equal to number of protons.
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true but R is not correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: (a) Both A and R are true and R is correct explanation of A
Q24. Assertion (A): Isotopes have different chemical properties.
Reason (R): Isotopes have same atomic number.
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true but R is not correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: (d) A is false but R is true
Q25. Assertion (A): Valency of neon is zero.
Reason (R): Neon has completely filled outermost shell.
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true but R is not correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: (a) Both A and R are true and R is correct explanation of A
Q26. Assertion (A): Rutherford’s model could not explain stability of atom.
Reason (R): Revolving electrons would lose energy and fall into nucleus.
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true but R is not correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: (a) Both A and R are true and R is correct explanation of A
Q27. Assertion (A): Maximum number of electrons in M-shell is 18.
Reason (R): Maximum number of electrons in a shell is given by 2n².
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true but R is not correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: (a) Both A and R are true and R is correct explanation of A
Q28. Assertion (A): Isobars have different atomic numbers.
Reason (R): Isobars belong to different elements.
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true but R is not correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: (a) Both A and R are true and R is correct explanation of A
Q29. Assertion (A): Mass of an atom resides mainly in nucleus.
Reason (R): Protons and neutrons are present in nucleus.
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true but R is not correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: (a) Both A and R are true and R is correct explanation of A
Q30. Assertion (A): Chlorine has fractional atomic mass 35.5 u.
Reason (R): Chlorine exists in isotopic forms.
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true but R is not correct explanation of A
c) A is true but R is false
d) A is false but R is true
Answer: (a) Both A and R are true and R is correct explanation of A
Q31. Which of the following statements are correct about electrons?
i) They are negatively charged
ii) They are present in the nucleus
iii) Their mass is negligible compared to proton
iv) They revolve around the nucleus
a) i, iii and iv
b) i and ii
c) ii and iii
d) i, ii, iii and iv
Answer: a) i, iii and iv
Q32. Which of the following statements are correct according to Thomson’s model of atom?
i) Atom is a positively charged sphere
ii) Electrons are embedded in the positive sphere
iii) Atom has a central nucleus
iv) Atom is electrically neutral
a) i, ii and iv
b) i and iii
c) ii and iii
d) i, ii, iii and iv
Answer: a) i, ii and iv
Q33. According to Rutherford’s experiment, which conclusions were correct?
i) Most of the space in atom is empty
ii) Positive charge occupies very little space
iii) Electrons are present in nucleus
iv) Nearly all mass is concentrated in nucleus
a) i and ii
b) i, ii and iv
c) ii and iii
d) i, ii, iii and iv
Answer: b) i, ii and iv
Q34. Which of the following statements are correct about Bohr’s model?
i) Electrons revolve in discrete orbits
ii) Electrons radiate energy while revolving
iii) Only certain orbits are allowed
iv) Electrons do not radiate energy in allowed orbits
a) i and ii
b) i, iii and iv
c) ii and iii
d) i, ii, iii and iv
Answer: b) i, iii and iv
Q35. Which of the following are sub-atomic particles?
i) Proton
ii) Neutron
iii) Electron
iv) Nucleus
a) i and ii
b) i, ii and iii
c) ii and iii
d) i, ii, iii and iv
Answer: b) i, ii and iii
Q36. Which of the following statements are correct about isotopes?
i) They have same atomic number
ii) They have different mass numbers
iii) They have different chemical properties
iv) They have same chemical properties
a) i and ii
b) i, ii and iv
c) ii and iii
d) i, ii, iii and iv
Answer: b) i, ii and iv
Q37. Which of the following are correct about isobars?
i) Same atomic number
ii) Same mass number
iii) Different atomic numbers
iv) Belong to different elements
a) i and ii
b) ii, iii and iv
c) i and iii
d) i, ii, iii and iv
Answer: b) ii, iii and iv
Q38. Which of the following statements are correct about valency?
i) It depends on outermost shell electrons
ii) Noble gases have zero valency
iii) Oxygen has valency 2
iv) Sodium has valency 2
a) i and ii
b) i, ii and iii
c) ii and iii
d) i, ii, iii and iv
Answer: b) i, ii and iii
Q39. Which of the following statements are correct about atomic number and mass number?
i) Atomic number = number of protons
ii) Mass number = protons + neutrons
iii) Atomic number = protons + neutrons
iv) Mass number is denoted by A
a) i and ii
b) i, ii and iv
c) ii and iii
d) i, ii, iii and iv
Answer: b) i, ii and iv
Q40. Which of the following statements are correct about electron distribution?
i) Maximum electrons in K-shell is 2
ii) Maximum electrons in L-shell is 8
iii) Maximum electrons in outermost shell is 8
iv) Shells are filled randomly
a) i and ii
b) i, ii and iii
c) ii and iii
d) i, ii, iii and iv
Answer: b) i, ii and iii
Q41. Match the following:
| Column I | Column II |
|---|---|
| (a) Electron | (i) Discovered by Chadwick |
| (b) Proton | (ii) Negatively charged |
| (c) Neutron | (iii) Discovered by Goldstein |
| (d) Canal rays | (iv) No charge |
Answer: a–ii, b–iii, c–iv, d–iii
Q42. Match the following:
| Column I | Column II |
|---|---|
| (a) Atomic number | (i) Protons + Neutrons |
| (b) Mass number | (ii) Protons |
| (c) Valency | (iii) Combining capacity |
| (d) Nucleons | (iv) Protons and Neutrons |
Answer: a–ii, b–i, c–iii, d–iv
Q43. Match the following:
| Column I | Column II |
|---|---|
| (a) K-shell | (i) 8 electrons |
| (b) L-shell | (ii) 2 electrons |
| (c) M-shell | (iii) 18 electrons |
| (d) Outermost shell | (iv) Maximum 8 electrons |
Answer: a–ii, b–i, c–iii, d–iv
Q44. Match the following:
| Column I | Column II |
|---|---|
| (a) Protium | (i) 3₁H |
| (b) Deuterium | (ii) 2₁H |
| (c) Tritium | (iii) 1₁H |
| (d) Hydrogen isotopes | (iv) Same atomic number |
Answer: a–iii, b–ii, c–i, d–iv
Q45. Match the following:
| Column I | Column II |
|---|---|
| (a) Rutherford | (i) Neutron |
| (b) J.J. Thomson | (ii) Nuclear model |
| (c) Chadwick | (iii) Electron |
| (d) Goldstein | (iv) Canal rays |
Answer: a–ii, b–iii, c–i, d–iv
Q46. Match the following:
| Column I | Column II |
|---|---|
| (a) Neon | (i) Valency 2 |
| (b) Oxygen | (ii) Valency 0 |
| (c) Magnesium | (iii) Valency 1 |
| (d) Sodium | (iv) Valency 2 |
Answer: a–ii, b–i, c–iv, d–iii
Q47. Match the following:
| Column I | Column II |
|---|---|
| (a) Isotopes | (i) Same mass number |
| (b) Isobars | (ii) Same atomic number |
| (c) Chlorine-35 | (iii) 17 protons |
| (d) Carbon-14 | (iv) 8 neutrons |
Answer: a–ii, b–i, c–iii, d–iv
Q48. Match the following:
| Column I | Column II |
|---|---|
| (a) Alpha particle | (i) Doubly charged helium ion |
| (b) Gold foil | (ii) Very thin metal sheet |
| (c) 180° deflection | (iii) Small dense nucleus |
| (d) Most particles passed | (iv) Empty space |
Answer: a–i, b–ii, c–iii, d–iv
Q49. Match the following:
| Column I | Column II |
|---|---|
| (a) Atomic number (Z) | (i) Denoted by A |
| (b) Mass number (A) | (ii) Denoted by Z |
| (c) Nitrogen | (iii) 14₇N |
| (d) Carbon | (iv) 6 protons |
Answer: a–ii, b–i, c–iii, d–iv
Q50. Match the following:
| Column I | Column II |
|---|---|
| (a) Complete octet | (i) Highly reactive |
| (b) Incomplete outer shell | (ii) Stable |
| (c) Bohr model | (iii) Discrete orbits |
| (d) Rutherford model | (iv) Electrons revolve around nucleus |
Answer: a–ii, b–i, c–iii, d–iv
SEBA Class 9 Science Chapter 4 Structure of the Atom MCQs (2026–27) Important Objective Questions
The SEBA Class 9 Science Chapter 4 Structure of the Atom MCQs are prepared strictly as per the latest ASSEB syllabus 2026–27. These SEBA Class 9 Science Chapter 4 Structure of the Atom MCQs include conceptual objective questions, theory-based MCQs, and board-oriented practice sets.
Students preparing for the board examination should regularly practice SEBA Class 9 Science Chapter 4 Structure of the Atom MCQs. These seba class 9 science chapter 4 mcqs cover important topics such as atomic models, subatomic particles, distribution of electrons in shells, valency, isotopes, and isobars.
The structure of the atom mcqs class 9 seba provided here are prepared by subject experts to ensure complete alignment with the latest exam pattern. These ASSEB class 9 science important MCQs help students understand atomic structure concepts clearly.
Regular revision of SEBA Class 9 Science Chapter 4 Structure of the Atom MCQs along with assam board class 9 science objective questions improves conceptual clarity, confidence, and scoring performance in the 2026–27 ASSEB board examination.
Frequently Asked Questions (FAQ)
1. Are these SEBA Class 9 Science Chapter 4 Structure of the Atom MCQs based on the latest syllabus?
Yes, these SEBA Class 9 Science Chapter 4 Structure of the Atom MCQs follow the latest ASSEB syllabus for 2026–27.
2. Are these seba class 9 science chapter 4 mcqs helpful for board exam preparation?
Yes, these seba class 9 science chapter 4 mcqs are designed according to the latest board exam pattern.
3. Do structure of the atom mcqs class 9 seba include questions on isotopes and isobars?
Yes, structure of the atom mcqs class 9 seba include questions on isotopes, isobars, and atomic number concepts.
4. Who prepared these ASSEB class 9 science important MCQs?
These ASSEB class 9 science important MCQs are prepared by subject experts of Assam Eduverse.
5. Are assam board class 9 science objective questions from Structure of the Atom frequently asked?
Yes, important assam board class 9 science objective questions from Structure of the Atom are frequently asked in examinations.
6. Which important topics are covered in Chapter 4 MCQs?
Topics include atomic models, subatomic particles, isotopes, isobars, atomic number, and mass number.
7. Can regular practice of SEBA Class 9 Science Chapter 4 Structure of the Atom MCQs improve scores?
Yes, regular practice improves conceptual clarity, accuracy, and board exam performance.
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