Atomic Structure MCQs
Question 1. The smallest part of an element that retains the chemical properties of the element is
(1) Electron
(2) Molecule
(3) Atom
(4) Proton
Answer: (4) Proton
Question 2. Electron was discovered by
(1) William Crookes
(2) A. Arrhenius
(3) Michael Faraday
(4) J. J. Thomson
Answer: (4) J. J. Thomson
Question 3. Cathode rays are composed of
(1) Radiation
(2) Thermal radiation
(3) Beam of negatively charged particles
(4) Positively charged particles
Answer: (3) Beam of negatively charged particles
Question 4. Cathode rays are deflected under the influence of electromagnetic fields because cathode rays are
(1) Electromagnetic radiation (EMR, i-e., light)
(2) Positively charged particles
(3) Beam of neutral particles
(4) Beam of electrons
Answer: (4) Beam of electrons
Question 5. In a perforated cathode ray tube, other rays other than cathode rays were found. These rays are
(1) Protons
(2) Electrons
(3) Radiation
(4) Neutrons
Answer: (3) Radiation
Question 6. Who among the following got Nobel Prize twice?
(1) Rutherford
(2) Bohr
(3) Einstein
(4) Marie Curie
Answer: (4) Marie Curie
Question 7. Radioactivity was discovered by
(1) Rutherford
(2) Becquerel
(3) Marie Curie
(4) Pierre Curie
Answer: (3) Marie Curie
Question 8. Radioactivity was first recognised while working with which element?
(1) Uranium
(2) Thorium
(3) Polonium
(4) Barium
Answer: (1) Uranium
Question 9. The concept of nucleus of an atom was given by
(1) J. J. Thomson
(2) Neils Bohr
(3) Rutherford
(4) M. Curie
Answer: (3) Rutherford
Question 10. The diameter of the nucleus is of the order of
(1)10–3cm
(2) 10–23cm
(3) 10–3 cm
(4) 10–13 cm
Answer: (4) 10–13 cm
Question 11. From the fact that a helium atom is four times as heavy as a. hydrogen atom, Rutherford predicted the existence of
(1) Proton
(2) Isotope
(3) Neutron
(4) Nucleus
Answer: (1) Proton
Question 12. From the study of sun spectra, the element first identified is
(1) Helium
(2) Hydrogen
(3) Uranium
(4) Gold
Answer: (1) Helium
Question 13. Which of the following concepts is not connected to Bohr’s model?
(1) Circular shell or orbit
(2) Quantization
(3) Line spectra of hydrogen
(4) Nuclear force
Answer: (2) Quantization
Question 14. An electron in a Bohr’s orbit is associated with definite
(1) Radius
(2) Velocity
(3) Energy
(4) All of the above
Answer: (3) Energy
Question 15. lonization energy of hydrogen atom, as calculated (by Bohr) and experimentally obtained, is
(1) 13.56 eV
(2) 13.56 J
(3) 13.56 Cal
(4) None of these
Answer: (1) 13.56 eV
Question 16. Which of the following is considered as a limitation of Bohr’s model? It wa unable to explain
(1) En , ie., energy of the nth shell electron of hydrogen
(2) Ionization energy of hydrogen
(3) Line spectrum of helium
(4) Line spectrum of hydrogen
Answer: (2) lonization energy of hydrogen
Question 17. On which of the following, Rutherford’s model differs from Bohr’s model?
(1) Circular shape of orbit
(2) Concept of the nucleus
(3) Empty space in an atom
(4) Stability of an atom
Answer: (4) Stability of an atom
Question 18. Which of the following is true?
(A = mass number, Z = atomic number, N = number of neutrons)
(1) A= Z
(2) A=Z-N
(3) A=Z+N
(4) A=N-Z
Answer: (3) A=Z+N
Question 19. Isotopes of an element have the same
(1) Mass number (A)
(2) Number of neutrons
(3) Number of protons
(4) Number of protons but not electrons
Answer: (3) Number of protons
Question 20. Isotopes are atoms with same number of
(1) Neutrons
(2) Protons
(3) Electrons
(4) Protons
Answer: (1) Neutrons
Question 21. Isobars are atoms having same number of
(1) Protons
(2) Nettvons
(3) Electrons
(4) Protons + Neutrons
Answer: (4) Protons + Neutrons
Question 22. Mass of a 12C isotope, in AMU unit is,
(1) 4
(2)12
(3) 1/12
(4) None of them
Answer: (2) 12
Question 23. The ground state electron configuration of potassium (Z = 19) is
(1) 2, 8, 8, 1
(2) 2, 8, 9,0
(3) 2, 9, 8, 0
(4) 2,7, 8, 2
Answer: (1) 2, 8, 8, 1
Question 24: Atoms of which element have no neutron?
(1) Oxygen
(2) Hydrogen
(3) Carbon
(4) Nitrogen
Answer: (2) Hydrogen
Question 25. Which force binds the nucleons?
(1) Gravitational force
(2) Electrostatic force
(e) Nuclear force
(4) None of these
Answer: (3) Nuclear force
Question 26. Which scientist first enunciated the atomic concept of matter?
(1) Newton
(2) Einstein
(3) Dalton
(4) None of these
Answer: (3) Dalton
Question 27. The atomic number is
(1) Mass of an atom x
(2) Total number of protons and neutrons
(3) Number of protons
(4) Number of neutrons
Answer: (3) Number of protons
Question 28. The maximum possible number of electrons in the outermost shell of an atom is
(1) 16
(2) 18
(3) 8
(4) 10
Answer: (3) 8
29. The magnitude of the negative charge an electron carries is
(1) 1.602 x 10–2 coulombs
(2) 0.602 x 10 –9 coulombs
(3) 1.602 x 10–19 coulombs
(4) 1.602 x 10–25 coulombs
Answer: (3) 1.602 x 10–19 coulombs
Question 30. If two isotopes of a certain element are known, it follows: that the atoms of the element
(1) Differ chemically frorn each other
(2) Have different numbers of electrons surrounding their nucle.
(3) Have different numbers of neutrons in their nuclei.
(4) Have the same mass number.
Answer: (3) Have different numbers of neutrons in their nuclei.
Question 31. Which of the following are examples of isotopes
(1) 14C and , 14N
(2) 40K and, 40Ca
(3) 8 16O and 8 18O
(4) None of these
Answer: (3) 8 16O and, 8 18O
Question 32. Sodium atom forms a cation by losing one electron. The cation will be
(1) S+
(2) Na+
(3) Kt+
(4) None of these
Answer: (2) Na+
Question 33. A deuteron contains
(1) A neutron and position
(2) A neutron and a proton
(3) A neutron and two protons
(4) A proton and two neutrons
Answer: (2) A neutron and a proton
Question 34. The nucleus of an atom contains
(1) Electrons
(2) Protons alone
(3) Neutrons alone
(4) Protons and neutrons
Answer: (4) Protons and neutrons
Question 35. The neutron was discovered by
(1) J .J. Thomson
(2) G. T. Seaborg
(3) E. Rutherford
(4) James Chadwick
Answer: (4) James Chadwick
Question 36. The number of electrons in the nucleus of 6C12 is
(1) 6
(2) 12
(3) 0
(4) 3
Answer: (3) 0
Question 37. Positron is
(1) _1 0e
(2) +10e
(3) 11H
(4) None of these
Answer: (2) +10e
Question 38. The average distance of an electron in an atom from its nucleus is of the order of
(1) 106m
(2) 10–6m
(3) 10–10m
(4) 10–15m
Answer: (3) 10–10 m
Question 39. A neutral atom (atomic no. > 1) contains
(1) Proton only
(2) Neutron + Proton
(3) Neutron + Electron
(4) Neutron + Proton + Electron
Answer: (4) Neutron + Proton + Electron
Question 40. The radius of an atom is of the order of
(1) 10–10cm
(2) 10–13cm
(3) 10–15cm
(4) 10–8cm
Answer: (4) 10–8 cm
Question 41. Chlorine atom differs from chlorine ion in the number of which of the following ?
(1) Protons
(2) Neutrons
(3) Electrons y
(4) Both Protons and Neutrons
Answer: (3) Electrons
Question 42. Neutrons are present inthe nuclei of all elements except
(1) Hydrogen
(2) Oxygen
(3) Deuterium
(4) Chlorine
Answer: (1) Hydrogen
Question 43. When electrons revolve in stationary orbits
(1) There is no change in energy level
(2) They become stationary
(3) They are gaining kinetic energy
(4) There is increase in energy
Answer: (1) There is no change in energy level
Question 44. Which of the following isoelectronic species has less electrons than protons?
(1) O2-
(2) F–
(3) Na+
(4) Mg2+
Answer: (1) O2-
Question 45. As we move away from the nucleus, the energy of an orbit
(1) Decreases
(2) Increases
(3) Remains unchanged
(4) None of these
Answer: (2) Increases
Question 46. By addition of one electron in the outermost shell of a chlorine atom, it produces a
(1) New atom
(2) Anion
(3) Cation
(4) No change
Answer: (2) Anion
Question 47. Nucleons are
(1) Only protons
(2) Only neutrons
(3) Protons and neutrons
(4) Protons, electrons and neutrons
Answer: (3) Protons and neutrons
Question 48. Rutherford’s a-particle scattering experiment led to the discovery of
(1) Electrons
(2) Protons
(3) Neutrons
(4) Atomic nucleus
Answer: (4) Atomic nucleus
Question 49. The electronic configuration of a sodium atom is
(1) 2, 8, 3
(2) 2, 8, 8
(3) 2, 8, 1
(4) 2,5, 3
Answer: (3) 2, 8, 1
Question 50. The valency of the element having electronic configuration 2, 8, 8, 1 is
(1) 1
(2) 2
(3) 3a
(4) 7
Answer: (1) 1
