# WBBSE Class 9 Physical Science MCQ Questions Chapter 4.1 Atomic Structure

Well structured WBBSE Class 9 Physical Science MCQ Questions Chapter 4.1 Ideas of History can serve as a valuable review tool before exams.

## Atomic Structure Class 9 WBBSE MCQ Questions

Multiple Choice Questions :

Question 1.
Atoms of which element have no neutron?
(i) Oxygen
(ii) Hydrogen
(iii) Carbon
(iv) Nitrogen
Hydrogen

Question 2.
Which force binds the nucleons ?
(i) Gravitational force
(ii) Electrostatic force
(iii) Nuclear force.
(iv) Electromagnetic force
Nuclear force.

Question 3.
Which scientist first enunciated the atomic concept of matter ?
(i) Newton
(ii) Einstein
(iii) Dalton
(iv) Rutherford
Dalton.

Question 4.
The atomic number is –
(i) mass of an atom
(ii) total number of protons and neutrons
(iii) number of protons
(iv) number of neutrons
Total number of protons and neutrons.

Question 5.
The maximum possible number of electrons in the outermost shell of an atom is –
(i) 16
(ii) 18
(iii) 8
(iv) 10
8.

Question 6.
The magnitude of the negative charge an electron carries is–
(i) 1.602 × 10-2 coulombs
(ii) 1.602 × 10-9 coulombs
(iii) 1.602 × 10-19 coulombs
(iv) 1.602 × 10-25 coulombs
1.602 × 10-19 coulombs.

Question 7.
If two isotopes of a certain element are known, it follows that the atoms of the element :
(i) differ chemically from each other
(ii) have different number of electrons surrounding their nuclei.
(iii) have different number of neutrons in their nuclei.
(iv) have the same mass number.
Have different number of neutrons in their nuclei.

Question 8.
which of the following are example of isotopes ?
(i) $${ }_6^{14} \mathrm{C}$$ and $${ }_7^{14} \mathrm{N}$$
(ii) $${ }_{19}^{40} \mathrm{K}$$ and $${ }_{20}^{40} \mathrm{Ca}$$
(iii) $${ }_8^{16} \mathrm{O}$$ and $${ }_8^{18} \mathrm{O}$$
(iv) $${ }_6^{14} \mathrm{C}$$ and $${ }_8^{16} \mathrm{O}$$
$${ }_8^{16} \mathrm{O}$$ and $${ }_8^{18} \mathrm{O}$$.

Question 9.
Sodium atom forms a cation by losing one electron. The cation will be :
(i) S+
(ii) Na+
(iii) K+
(iv) H+
Na+

Question 10.
A deutron contains –
(i) a neutron and a positron
(ii) a neutron and a proton
(iii) a neutron and two protons
(iv) a proton and two neutrons
A neutron and a proton.

Question 11.
The nucleus of an atom contains –
(i) electrons
(ii) protons alone
(iii) neutrons alone
(iv) protons and neutrons
Protons and neutrons.

Question 12.
The neutron was discovered by –
(i) J. J. Thomson
(ii) G.T. Seaborg
(iii) E. Rutherford

Question 13.
The number of electrons in the nucleus of $${ }_6^{12} \mathrm{C}$$ is –
(i) 6
(ii) 12
(iii) 0
(iv) 3
0.

Question 14.
Positron is – (i) $${ }_{-1}^0 \mathrm{e}$$
(ii) $${ }_{+1}^0 \mathrm{e}$$
(iii) $${ }_{+1}^1 \mathrm{H}$$
(iv) None of these
$${ }_{+1}^0 \mathrm{e}$$.

Question 15.
The average distance of an electron in an atom from its nucleus is in the order of :
(i) 106 m
(ii) 10-6 m
(iii) 10-10 m
(iv) 10-15 m
10-10 m.

Question 16.
A neutral atom (atomic no. > 1) contains
(i) Proton oniy
(ii) Neutron + Proton
(iii) Neutron + Electron
(iv) Neutron + Proton + Electron
Neutron + Proton + Electron

Question 17.
The radius of an atom is in the order of –
(i) 10-16 cm
(ii) 10-13 cm
(iii) 10-15 cm
(iv) 10-8 cm
10-8 cm}.

Question 18.
Chlorine atom differs from chlorine ion in the number of which of the following :
(i) Protons
(ii) Neutrons
(iii) Electrons
(iv) Both Protons and Neutrons
Electrons.

Question 19.
Neutrons are present in the nuciei of all elements except –
(i) Hydrogen
(ii) Oxygen
(iii) Deuterium
(iv) Chlorine
Hydrogen.

Question 20.
When electrons revolve in stationary orbits –
(i) there is no change in energy level
(ii) they become stationary
(iii) they are gaining kinetic energy
(iv) there is increase in energy
There is no change in energy level.

Question 21.
Which of the following isoelectronic species has less electrons than protons ?
(i) O2-
(ii) F
(iii) Na*
(iv) Mg2+
O2-.

Question 22.
As we move away from the nucleus, the energy of an orbit –
(i) decreases
(ii) increases
(iii) remains unchanged
(iv) none of these
increases.

Question 23.
If one electron is added to the outermost shell of a chlorine atom, it produces a –
(i) new atom
(ii) anion
(iii) cation
(iv) there will be no change
anion

Question 24.
Neucleons are –
(i) only protons
(ii) only neutrons
(iii) protons and neutrons
(iv) protons, electrons and neutrons
protons and neutrons.

Question 25.
Rutherford’s α-particle scattering experiment led to the discovery of
(i) electrons
(ii) protons
(iii) neutrons
(iv) atomic neucleus
atomic neucleus

Question 26.
The electronic configuration of sodium atom is –
(i) 2,8,3
(ii) 2,8,8
(iii) 2,8,1
(iv) 2,5,3
2,8,1

Question 27.
The valency of the element having electronic configuration 2,8,8,1 is-
(i) 1
(ii) 2
(iii) 3
(iv) 7
1

Fill in the blanks :

1. Most part of an atom is _____.
vacant or empty.

2. The number of protons in an atom of an element is the ______ number.
atomic.

3. Atom is the smallest part of an _______ that participates in chemical reactions but does not usually exist freely in nature.
element.

3. Chemical combination takes place by the union of ______ number of atoms of the elements in simple ratios 1: 3,2: 3,1: 2 etc.
integral.

4. Only the nucleus of ordinary _______ does not contain any neutron.
hydrogen.

5. Constituents of the nucleus are called ______.
nucleons.

6. An ion is an atom or a group of atoms that carries ______ charge.
electric.

7. Since the mass of ______ is negligibly small, the whole mass of an atom is supposed to be concentrated at its nucleus.
electrons.

8. isotope are the atoms of the same element which have the same _______ number but different mass number.
atomic.

9. The tota! number of electrons present in all the shells of an atom is equal to the number of ______ present in its nucieus.
protons.

10. Round the nucleus, negatively charged particles called _______ revolve in different paths.
electrons.

11. Nuclear force is a _______ attractive torce active within the range of 2 × 10-15 metre that acts between the nucieons.
short range.

12. The nucleus of an atom is _______ charged.
positively.

13. The outermost orbit of an atom can possess maximum _______ electrons.

14. To calculate the number of neutrons in an atom, we substract its ________ from its mass number.
atomic number.

15. The whole mass and positive charges of an atom remain confined to its _______.
nucleus.

16. For the isotope $${ }_6^{13} \mathrm{C}$$, the number of neutrons is ______
7.

17. The atomic number of an atom of an element is the number of ______ in its nucleus.
protons.

18. The maximum capacity of a shell to accommodate electrons is given by the general rule _______.
2 n2.

19. The atomic number of potassium is _______.
19.

20. Hydrogen has ______ isotopes.
three.

21. _______ recognised that an element might have atoms of identical chemical properties but of different atomic weights.
Soddy.

22. An electron has wave as well as ________ nature.
particle.

23. A proton is ______ times heavier than an electron.
1837.

24. An ______ is a well-defined circular path in which the electron revolves.
orbit.

25. The lowest energy level in an atom is _______ level.
K.

26. Electrically charged atoms are called _______.
ions.

27. The particles, which Thomson called corpuscles, later came to known as ______.
electrons.

28. Becquerel put small crystals of _______ upon the black paper.
Potassium uranyl sulphate [K(UO2)(SO4)3.3H2 O]

29. The diameter of the atom is about while that of the nucleus is -.
10-8 cm}, 10-13 cm}

30. 114 Be + 42 He ______ + 10n.
$${ }_6^{14} \mathrm{C}$$ →

31. The definite small quantity of energy is known as energy –
quanta.

32. The radius of nucleus is – time less than that of the atom.
105.

33. The particles in the nucleus are called