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
Answer:
Hydrogen
Question 2.
Which force binds the nucleons ?
(i) Gravitational force
(ii) Electrostatic force
(iii) Nuclear force.
(iv) Electromagnetic force
Answer:
Nuclear force.
Question 3.
Which scientist first enunciated the atomic concept of matter ?
(i) Newton
(ii) Einstein
(iii) Dalton
(iv) Rutherford
Answer:
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
Answer:
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
Answer:
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
Answer:
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.
Answer:
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 \({ }_8^{16} \mathrm{O}\)
Answer:
\({ }_8^{16} \mathrm{O}\) 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+
Answer:
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
Answer:
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
Answer:
Protons and neutrons.
Question 12.
The neutron was discovered by –
(i) J. J. Thomson
(ii) G.T. Seaborg
(iii) E. Rutherford
(iv) James Chadwick
Answer:
James Chadwick.
Question 13.
The number of electrons in the nucleus of \({ }_6^{12} \mathrm{C}\) is –
(i) 6
(ii) 12
(iii) 0
(iv) 3
Answer:
0.
Question 14.
Positron is – (i) \({ }_{-1}^0 \mathrm{e}\)
(ii) \({ }_{+1}^0 \mathrm{e}\)
(iii) \({ }_{+1}^1 \mathrm{H}\)
(iv) None of these
Answer:
\({ }_{+1}^0 \mathrm{e}\).
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
Answer:
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
Answer:
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
Answer:
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
Answer:
Electrons.
Question 19.
Neutrons are present in the nuciei of all elements except –
(i) Hydrogen
(ii) Oxygen
(iii) Deuterium
(iv) Chlorine
Answer:
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
Answer:
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+
Answer:
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
Answer:
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
Answer:
anion
Question 24.
Neucleons are –
(i) only protons
(ii) only neutrons
(iii) protons and neutrons
(iv) protons, electrons and neutrons
Answer:
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
Answer:
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
Answer:
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
Answer:
1
Fill in the blanks :
1. Most part of an atom is _____.
Answer:
vacant or empty.
2. The number of protons in an atom of an element is the ______ number.
Answer:
atomic.
3. Atom is the smallest part of an _______ that participates in chemical reactions but does not usually exist freely in nature.
Answer:
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.
Answer:
integral.
4. Only the nucleus of ordinary _______ does not contain any neutron.
Answer:
hydrogen.
5. Constituents of the nucleus are called ______.
Answer:
nucleons.
6. An ion is an atom or a group of atoms that carries ______ charge.
Answer:
electric.
7. Since the mass of ______ is negligibly small, the whole mass of an atom is supposed to be concentrated at its nucleus.
Answer:
electrons.
8. isotope are the atoms of the same element which have the same _______ number but different mass number.
Answer:
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.
Answer:
protons.
10. Round the nucleus, negatively charged particles called _______ revolve in different paths.
Answer:
electrons.
11. Nuclear force is a _______ attractive torce active within the range of 2 × 10-15 metre that acts between the nucieons.
Answer:
short range.
12. The nucleus of an atom is _______ charged.
Answer:
positively.
13. The outermost orbit of an atom can possess maximum _______ electrons.
Answer: eight.
14. To calculate the number of neutrons in an atom, we substract its ________ from its mass number.
Answer:
atomic number.
15. The whole mass and positive charges of an atom remain confined to its _______.
Answer:
nucleus.
16. For the isotope \({ }_6^{13} \mathrm{C}\), the number of neutrons is ______
Answer:
7.
17. The atomic number of an atom of an element is the number of ______ in its nucleus.
Answer:
protons.
18. The maximum capacity of a shell to accommodate electrons is given by the general rule _______.
Answer:
2 n2.
19. The atomic number of potassium is _______.
Answer:
19.
20. Hydrogen has ______ isotopes.
Answer:
three.
21. _______ recognised that an element might have atoms of identical chemical properties but of different atomic weights.
Answer:
Soddy.
22. An electron has wave as well as ________ nature.
Answer:
particle.
23. A proton is ______ times heavier than an electron.
Answer:
1837.
24. An ______ is a well-defined circular path in which the electron revolves.
Answer:
orbit.
25. The lowest energy level in an atom is _______ level.
Answer:
K.
26. Electrically charged atoms are called _______.
Answer:
ions.
27. The particles, which Thomson called corpuscles, later came to known as ______.
Answer:
electrons.
28. Becquerel put small crystals of _______ upon the black paper.
Answer:
Potassium uranyl sulphate [K(UO2)(SO4)3.3H2 O]
29. The diameter of the atom is about while that of the nucleus is -.
Answer:
10-8 cm}, 10-13 cm}
30. 114 Be + 42 He ______ + 10n.
Answer:
\({ }_6^{14} \mathrm{C}\) →
31. The definite small quantity of energy is known as energy –
Answer:
quanta.
32. The radius of nucleus is – time less than that of the atom.
Answer:
105.
33. The particles in the nucleus are called
Answer:
Nucleons