Mock Test - Structure of the Atom

Revise Class 9 Science – Structure of the Atom with Our MCQ Mock Test!

Do you know how protons, neutrons, and electrons are arranged inside an atom? Test your understanding with this MCQ-based mock test on Structure of the Atom, designed as per the latest Class 9 Science syllabus. This test covers all essential topics — discovery of subatomic particles, Thomson’s, Rutherford’s, and Bohr’s models of the atom, atomic number, mass number, isotopes, and isobars.

Each question is carefully selected to help you recall key concepts, apply scientific reasoning, and prepare for exams effectively. With this test, you can assess your grasp of the chapter, improve speed and accuracy, and boost your confidence for school and board-level assessments.

Attempt now and make “Structure of the Atom” your strongest topic in Class 9 Science!

1. Which of the following does not have 8 valence electrons?

2. The isotopes of hydrogen which contain same number of electrons, protons and neutrons

Protium

Deuterium

Tritium

None of these

3. Which of the following is correct about particles of an atom?

Electron has positive charge and a mass much less than a neutron

Electron has a negative charge and a mass equal to mass of proton

Proton has positive charge and mass larger than mass of neutron

Neutron is neutral and has mass larger than the mass of electron.

4. Which of the following pairs have identical values of charge/mass?

A proton and a deuterium

A proton and a neutron

A deuterium and an α-particle

An electron and γ-rays

5. Which question Rutherford’s model failed to answer?

What causes the atoms to electrically neutral?

Where are electrons, protons and neutrons located in the nucleus?

Why is it easier to remove an electron from an atom as compound to proton?

If electron revolve continuously, why do they not lose energy and collapse in the nucleus?

6. The electronic configuration of Rb(37) will be

2, 8, 18, 9

2, 8, 18, 8, 1

2, 8, 8, 18, 1

2, 8, 18, 1, 8

7. Which part of Bohr’s model of atomic structure explains why electrons do not crash into the nucleus?

Electrons are always repelled by the nucleus.

Electrons are much farther from the nucleus.

Electrons keep gaining energy while revolving

Electrons revolve in orbit that have specific energy.

8. The ion of an element has 3 positive charges. Mass number of the atom is 27 and the number of neutrons is 14. What is the number of electrons in the ion?

9. S(16) has electronic configuration

2, 8, 6

2, 8, 8

2, 6, 7

2, 8, 4, 2

10. Isotopes of an element have

Same physical properties.

Different chemical properties.

Different number of neutrons.

Different atomic numbers.

11. Rutherford’s alpha (α) particles scattering experiment resulted into discovery of

Electron

Proton

Nucleus in the atom

Atomic Mass

12. Nucleus has

only protons

only neutrons

neutrons and protons

electrons, protons and neutrons.

13. How the sub atomic particles like proton is different from electron?

An electron is much heavier than a proton

An electron carries more charge than a proton

A proton is easily removed from an atom, but not an electron

A proton is positively charged, whereas an electron is negatively charged.

14. An atom has 4 electrons and 4 protons and 4 neutrons. The atom is electrically neutral. Which difference in the properties of protons and electrons affects the electrical neutrality of the atom?

Electrons are 2000 times lighter than protons.

Electrons and protons have the same charge and mass.

Electrons and protons have opposite charges of the same magnitude.

Electrons are present in the outer side of the atom compared to the protons.

15. When a gold sheet is bombarded by a beam of α-particles, only a few of them got deflected whereas most go straight, undeflected. This is because

the force of attraction exerted on α-particles by electrons is insufficient

the volume of nucleus is smaller than that of atom

the force of repulsion acting on fast moving α-particles is very small

the neutrons have no effect on α-particles.

16. Na⁺ has 12 neutrons and 10 electrons. Which of the following statement is correct?

Na+ has atomic number equal to 10 and mass number 22

Na+ has atomic number equal to 11 and mass number 23

Na+ has atomic number equal to 10 and mass number 23

Na+ has atomic number equal to 11 and mass number 22

17. The formula of molecules of x₂. One molecule of x₂ contains 18 protons. The mass number of X is 19. How many neutrons are present in one atom of x.

18. A student weighs 30 kg. Suppose his body is entirely made up of electrons. How many electrons are there in his body?

3.29 × 10³¹

3.29 × 10²³

3.29 × 10³⁰

3.29 × 10³²

19. Which of the following statement is correct about proton?

It is a nucleus of deuterium

It is an ionised hydrogen atom

It is an ionised hydrogen molecule

α-Particles consist of He+ ions

20. Identify the Mg²⁺ ion from the figure where, n and p represent the number of neutrons and protons respectively

21. Rutherford’s α-particle scattering experiment showed that
(i) electrons have negative charge
(ii) the mass and positive charge of the atom is concentrated in the nucleus
(iii) neutron exists in the nucleus
(iv) most of the space in atom is empty
Which of the above statements are correct?

(i) and (iii)

(ii) and (iv)

(i) and (iv)

(iii) and (iv)

22. Dalton’s atomic theory successfully explained

(i) Law of conservation of mass

(ii) Law of constant composition

(iii) Law of radioactivity

(iv) Law of multiple proportion

(i), (ii) and (iii)

(i), (iii) and (iv)

(ii), (iii) and (iv)

(i), (ii) and (iv)

23. In the Thomson’s model of atom, which of the following statements are correct?

(i) the mass of the atom is assumed to be uniformly distributed over the atom

(ii) the positive charge is assumed to be uniformly distributed over the atom

(iii) the electrons are uniformly distributed in the positively charged sphere

(iv) the electrons attract each other to stabilise the atom

(i), (ii) and (iii)

(i) and (iii)

(i) and (iv)

(i), (iii) and (iv)

24. An element has 3 valence electrons in its outermost 3rd shell, the name of element is

25. If K, L, M N, shells of an atom are full. The total number of electrons in that atom are :

26. Which of the following element with 2 valence electrons is inert?

27. How many electrons, protons and neutrons will be present in X^–, if atomic number of X is 9 and mass number is 19 ?

E = 9, P = 9, N = 10

E = 10, P = 9, N = 10

E = 10, P = 10, N = 10

E = 9, P = 10, N = 10

28. The charge/mass ratio of electron

depends upon nature of gas

depends upon nature of electrodes

remains constant

depends upon both nature of gas and nature of electrodes.

29. Which of the following statement(s) is/are incorrect for anode rays?

They are deflected by electric and magnetic fields.

Their charge/mass ratio depends upon the gas in the discharge tube used to produce anode rays.

The charge/mass ratio of particles in anode rays is constant.

They are produced by ionisation of gas in the discharge tube.

30. If K, L, M N, shells of an atom are full. The total number of electrons in that atom are :

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