MCQ Questions for Class 9 Science: Ch 4 Structure of the Atom

MCQ Questions for Class 9 Science: Ch 4 Structure of the Atom

1. When alpha-particles are sent through a thin metal foil, most of them go straight through the foil because 
(a) alpha-particles are positively charged
(b) alpha-particles are much smaller than electrons
(c) alpha-particles move with low velocity
(d) most part of the atom is empty
► (d) most part of the atom is empty

2. The number of electrons in an atom of Fluorine is 9. Its electronic configuration is _______.
(a) 8, 1
(b) 7, 2
(c) 2, 7
(d) 1, 8
► (c) 2, 7

3. N shell can have a maximum of _______ electrons.
(a) 32
(b) 2
(c) 18
(d) 8
► (a) 32

4. Rutherford’s scattering experiment falls for very small scattering angles because
(a) the impact parameter between the a-particle source and the nucleus of target is very large as compared to the size of nucleus.
(b) whole nuclear charge of the target atom is not screened by its electrons at all 
(c) the velocity of a-particles is large
(d) the gold foil is thin
► (b) whole nuclear charge of the target atom is not screened by its electrons at all 

5. Nucleous consist of:
(a) Proton and electron
(b) Proton and neutron
(c) Neutron and electron
(d) Only neutron
► (b) Proton and neutron

6. Which of the following is the correct electronic configuration for magnesium?
(a) 2, 8, 1
(b) 2, 8, 3
(c) 2, 8, 4
(d) 2, 8, 2
► (d) 2, 8, 2

7. The electronic configuration of an atom with atomic number 19 is:
(a) 2, 8, 8, 1
(b) 1, 2, 2, 8
(c) 2, 8, 9
(d) 2, 10, 7
► (a) 2, 8, 8, 1

8. Which of the following pairs have identical values of charge/mass? 
(a) A proton and a deuterium 
(b) A proton and a neutron 
(c) A deuterium and an a-particle 
(d) An electron and y-rays
► (c) A deuterium and an a-particle 

9. If Z = 6, what would be the valency of the element?
(a) 6
(b) 2
(c) 4
(d) 8
► (c) 4

10. An atom with 3 protons and 4 neutrons will have a valency of 
(a) 3
(b) 7
(c) 1
(d) 4
► (c) 1

11. Bohr proposed that while revolving in discrete orbits, the electrons:
(a) Gain energy
(b) Lose energy
(c) Do not radiate energy
(d) First lose energy and then gain energy.
► (c) Do not radiate energy

12. An neutral element A has 3 electrons, the atomic number of an element is _______.
(a) 1
(b) 2
(c) 5
(d) 3
► (d) 3

13. Lighest particle is –
(a) Neutron
(b) Electron
(c) Proton
(d) None of these
► (b) Electron

14. Argon has atomic number of 18 and mass number of 40. Calcium has atomic 20 and mass number 40. Calcium and argon are examples of _______.
(a) isotopes
(b) isobars
(c) isotones
(d) isochores
► (b) isobars

15. The number of valence electron in Na is –
(a) 1
(b) 2
(c) 3
(d) 4
► (a) 1

16. Why do isotopes have different physical properties?
(a) Isotopes of an element have different electronic configuration.
(b) Isotopes have same atomic number.
(c) Isotopes of an element have different mass number.
(d) Isotopes of an element have different atomic number.
► (c) Isotopes of an element have different mass number.

17. The electronic configuration of Rb(37) will be 
(a) 2 , 8 , 1 8 , 9 
(b) 2 , 8 , 1 8 , 8 , 1 
(c) 2, 8,8 ,1 8,1 
(d) 2 ,8 ,1 8 ,1 ,8
► (b) 2 , 8 , 1 8 , 8 , 1 

18. Mass number of element is –
(a) Number of protons in its nucleus
(b) Number of electrons and protons in the atom
(c) Number of neutrons and protons in the nucleus
(d) Number of neutrons in the nucleus
► (c) Number of neutrons and protons in the nucleus

19. When a gas at reduced pressure is subjected to an electric discharge, the rays orignating from the negative electrode are–
(a) Cathode rays
(b) Anode rays
(c) x-rays
(d) Radiation ray
► (a) Cathode rays

20. The increasing order of the energy levels in an atom is _______ .
(a) K > L > M > N
(b) L > M > N > K
(c) L < M < N < K
(d) K < L < M < N
► (d) K < L < M < N

21. Atomic number is equal to:
(a) Number of protons + Number of electrons
(b) Number of protons
(c) Number of protons + Number of neutrons
(d) Number of neutrons
► (b) Number of protons

22. Neutron is a fundamental particle which have–
(a) +1 unit charge and 1 unit mass
(b) No charge and 1 unit mass
(c) Have no charge and mass
(d) Have –1 unit charge and 1 unit mass
► (b) No charge and 1 unit mass

23. The atomic number of an element having mass number 23 and number of neutron 12 is ________.
(a) 23
(b) 11
(c) 12
(d) 35
► (b) 11

24. Which form of iodine is used for the treatment of goiter?
(a) An isotone
(b) An isobar
(c) An isochore
(d) An isotope
► (d) An isotope

25. According to the Dalton's atomic theory –
(a) Electrons, proton and neutron are found in atom
(b) Atom is indivisible
(c) Atom of various element have same properties
(d) Atoms are destroyed in the chemical reaction
► (b) Atom is indivisible

26. The maximum number of electrons that can be accomodated in an orbit is given by the formula _______ where n is the number of orbit.​
(a) 2n + 2
(b) 2(n + 2)
(c) 2/n2
(d) 2n2
►(d) 2n2

27. An atom which has a mass number of 14 or 8 neutrons is–
(a) Isotope of oxygen
(b) Isobar of oxygen
(c) Isotope of carbon
(d) Isobar of carbon
► (c) Isotope of carbon

28. What is a valence shell?
(a) Third shell
(b) First shell
(c) Outermost shell
(d) Second shell
► (c) Outermost shell

29. The electron should be filled in the orbital in accordance with the increasing order of their energy. This statement is related with
(a) Affbau principle
(b) Pauli principle
(c) Hund's principle
(d) Plank's rules
► (a) Affbau principle

30. Which of the following statement is always correct? 
(a) An atom has equal number of electrons and protons. 
(b) An atom has equal number of electrons and neutrons. 
(c) An atom has equal number of protons and neutrons. 
(d) An atom has equal number of electrons, protons and neutron
► (a) An atom has equal number of electrons and protons. 
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