MCQ Questions for Class 9 Science Chapter 4 Structure of the Atom

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MCQ Questions for Class 9 Science Chapter 4 Structure of the Atom help to improve problem solving skills and promote active learning. This type of question is often used in exams, and practicing with them can help you get the highest marks possible.

Chapter 4 Class 9 Science CBSE MCQ Questions with answers play a very significant role in your final preparation for the exams. They help to identify the areas where the students need more work.

Chapter 4 Structure of the Atom Class 9 Science MCQ Questions

1. An atomic number of an element equals to what present in the nucleus of its atom?
(a) Protons
(b) Electrons
(c) Both of them
(d) None of them
▶ (a) Protons

2. 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.
(a) (i), (ii) and (iii)
(b) (i), (iii) and (iv)
(c) (ii), (iii) and (iv)
(d) (i), (ii) and (iv)
▶ (d) (i), (ii) and (iv)

3. The electron distribution in an aluminium atom is
(a) 2, 8, 3
(b) 2, 8, 2
(c) 8, 2, 3
(d) 2, 3, 8
▶ (a) 2, 8, 3

4. In a sample of ethylethanoate (CH3COOC2H5) the two oxygen atoms have the same number of electrons but different number of neutrons. Which of the following is the correct reason for it?
(a) One of the oxygen atoms has gained electrons.
(b) One of the oxygen atoms has gained two neutrons.
(c) The two oxygen atoms are isotopes.
(d) The two oxygen atoms are isobars.
▶ (c) The two oxygen atoms are isotopes.

5. Atomic models have been improved over the years. Arrange the following atomic models in the order of their chronological order
(i) Rutherford’s atomic model
(ii) Thomson’s atomic model
(iii) Bohr’s atomic model
(b) (ii), (iii) and (i)
(a) (i), (ii) and (iii)
(c) (ii), (i) and (iii)
(d) (iii), (ii) and (i)
▶ (c) (ii), (i) and (iii)

6. In 1932, J. Chadwick discovered another sub-atomic particle which had no charge and a mass nearly equal to that of a proton. It was eventually named as
(a) proton
(b) neutron
(c) electron
(d) α-particle
▶ (b) neutron

7. Mass of proton is
(a) equal to the mass of hydrogen atom
(b) less than the mass of hydrogen atom
(c) negligible
(d) more than the mass of hydrogen atom
▶ (a) equal to the mass of hydrogen atom

8. The nucleon number of the bromine atom is 79 and its proton number is 35. Which of the following is true about the bromine atom?
(a) It has 79 neutrons.
(b) It has 44 electrons.
(c) Its electronic configuration contains three shells which has 7 electrons in outermost shell.
(d) It has similar chemical properties as chlorine.
▶ (d) It has similar chemical properties as chlorine.

9. Which of the following is a property of isotopes?
(a) They have the same number of electrons.
(b) They have different numbers of protons.
(c) They have different chemical properties.
(d) They have the same mass number.
▶ (a) They have the same number of electrons.

10. The electronic configuration of elements A, B, C and D are (2, 8, 1), (2, 8, 2), (2, 8, 6) and (2, 8, 7) respectively. Which of them can make an ion with two negative charges?
(a) A
(b) B
(c) C
(d) D
▶ (c) C

11. 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.
(a) (i), (ii) and (iii)
(b) (i) and (iii)
(c) (i) and (iv)
(d) (i), (iii) and (iv)
▶ (a) (i), (ii) and (iii)

12. 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?
(a) 13
(b) 10
(c) 14
(d) 16
▶ (b) 10

13. The main drawback of Rutherford’s model of the atom is that
(a) it does not explain the stability of atom
(b) it does not show the location of protons
(c) it does not explain neutral nature of an atom
(d) it does not explain existence of a nucleus in an atom.
▶ (a) it does not explain the stability of atom

14. A neutral atom (atomic number > 1) has
(a) electron and proton
(b) neutron and electron
(c) neutron, electron and proton
(d) neutron and proton
▶ (c) neutron, electron and proton

15. Isotopes have
(a) same physical and chemical properties
(b) same physical properties but different chemical properties
(c) same chemical properties but different physical properties
(d) different physical and chemical properties
▶ (c) same chemical properties but different physical properties

16. Rutherford concluded from the α-particle scattering experiment that
(i) most of the space inside the atom is empty because most of the α-particles passed through the gold foil without getting deflected.
(ii) very few particles were deflected from their path, indicating that the negative charge of the atom occupies very little space.
(iii) a very large fraction of α-particles were deflected by 180°, indicating that all the negative charge and mass of the gold atom were not concentrated in a very small volume within the atom.
Identify the incorrect statements.
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (i), (ii) and (iii)
▶ (b) (ii) and (iii)

17. Rutherford’s experiment on scattering of α-particles showed for the first time that the atom has
(a) nucleus
(b) electron
(c) proton
(d) neutron
▶ (a) nucleus

18. Atom X and atom Y have similar chemical properties. If the proton number of atom X is 12, What is the likely proton number of atom Y ?
(a) 5
(b) 10
(c) 14
(d) 20
▶ (d) 20

19. The ion of an element has 2 positive charge. Mass number of the atom is 24 and the number of neutrons is 12. What is the number of electrons in the ion?
(a) 8
(b) 10
(c) 12
(d) 24
▶ (b) 10

20. Which of the following statements are part of Bohr’s model of hydrogen atom?
(a) Energy of the electrons in the orbit is quantized.
(b) The electron in the orbit nearest to the nucleus has the lowest energy.
(c) Electrons revolve in different orbits around the nucleus.
(d) All of these
▶ (d) All of these

21. The relative atomic mass of naturally occurring chlorine is not a whole number. What is the reason for this?
(a) Chlorine atoms can have different numbers of neutrons.
(b) Naturally occurring chlorine cannot be obtained pure.
(c) Chlorine is unstable.
(d) The mass of the electrons has been included.
▶ (a) Chlorine atoms can have different numbers of neutrons.

22. Cathode rays are made up of
(a) positively charged particles
(b) negatively charged particles
(c) neutral particles
(d) none of these
▶ (b) negatively charged particles

23. Which of the following electronic configurations is wrong?
(a) Li (3) = 2, 1
(b) O (3) = 2, 6
(c) S (16) = 2, 6, 8
(d) P (15) = 2, 8, 5
▶ (c) S (16) = 2, 6, 8

24. Which of the following particles is not deflected by a magnetic field?
(a) Proton
(b) Neutron
(c) Electron
(d) All of these
▶ (b) Neutron

25. Rutherford’s alpha particle scattering experiment eventually led to the conclusion that
(a) mass and energy are related
(b) nucleus is present in the centre of the atom
(c) neutrons are buried deep in the nucleus
(d) the point of impact with matter can be precisely determined.
▶ (b) nucleus is present in the centre of the atom

26. The element with the atomic number 3 is likely to have similar chemical properties to the element with the atomic number
(a) 5
(b) 11
(c) 8
(d) 20
▶ (b) 11

27. Neutrons are present in the nucleus of all atoms, except
(a) hydrogen
(b) helium
(c) lithium
(d) boron
▶ (a) hydrogen

28. Which of the following has the same number of electrons as an oxide ion (O2-)?
(a) K+
(b) Mg2+
(c) Cl
(d) S2-
▶ (b) Mg2+

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