CBSE Class 12 Physics Atoms MCQs Set A

Question : According to classical theory, the path of an electron in Rutherford atomic model is
(a) spiral
(b) circular
(c) parabolic
(d) straight line

Answer: A

Question : Rutherford’s a-particle experiment showed that the atoms have
(a) Proton
(b) Nucleus
(c) Neutron
(d) Electrons

Answer: B

Question : Rutherford’s atomic model was unstable because
(a) nuclei will break down
(b) electrons do not remain in orbit
(c) orbiting electrons radiate energy
(d) electrons are repelled by the nucleus

Answer: B

Question : According to Bohr’s model of hydrogen atom
(a) the linear velocity of the electron is quantised
(b) the angular velocity of the electron is quantised
(c) the linear momentum of the electron is quantised
(d) the angular momentum of the electron is quantised

Answer: D

Question : As the quantum number increases, the difference of energy between consecutive energy levels
(a) remain the same
(b) increases
(c) decreases
(d) sometimes increases and sometimes decreases.

Answer: C

Question : When hydrogen atom is in its first excited level, it’s radius is
(a) four times, it ground state radius
(b) twice times, it ground state radius
(c) same times, it ground state radius
(d) half times, it ground state radius.

Answer: A

Question : Which of the following series in the spectrum of hydrogen atom lies in the visible region of the electromagnetic spectrum?
(a) Paschen series
(b) Balmer series
(c) Lyman series
(d) Brackett series

Answer: B

Question : The Balmer series for the H-atom can be observed
(a) if we measure the frequencies of light emitted when an excited atom falls to the ground state
(b) if we measure the frequencies of light emitted due to transitions between excited states and the first excited state
(c) in any transition in a H-atom
(d) None of these

Answer: B

Question : In a hydrogen atom, which of the following electronic transitions would involve the maximum energy change
(a) n = 2 to n = 1
(b) n = 3 to n = 1
(c) n = 4 to n = 2
(d) n = 3 to n = 2

Answer: B

Question : The Lyman transitions involve
(a) largest changes of energy
(b) smallest changes of energy
(c) largest changes of potential energy
(d) smallest changes of potential energy

Answer: A 

Question : In the hydrogen atom, an electron makes a transition from n : 2 to n : 1. The magnetic field produced by the circulating electron at the nucleus
(a) decreases 16 times
(b) increases 4 times
(c) decreases 4 times
(d) increases 32 times 

Answer: D

Question : The ionization energy of hydrogen atom is 13.6 eV. Following Bohr’s theory, the energy corresponding to a transition between 3rd and 4th orbit is
(a) 3.40 eV
(b) 1.51 eV
(c) 0.85 eV
(d) 0.66 eV

Answer: D

Question : The largest wavelength in the ultraviolet region of the hydrogen spectrum is 122 nm. The smallest wavelength in the infrared region of the hydrogen spectrum (to the nearest integer) is
(a) 802 nm
(b) 823 nm
(c) 1882 nm
(d) 1648 nm

Answer: B

Question : Out of the following which one is not a possible energy for a photon to be emitted by hydrogen atom according to Bohr’s atomic model?
(a) 1.9 eV
(b) 11.1 eV
(c) 13.6 eV
(d) 0.65 eV

Answer: B

Question : If 13.6 eV energy is required to ionize the hydrogen atom, then the energy required to remove an electron from n : 2 is
(a) 10.2 eV
(b) 0 eV
(c) 3.4 eV
(d) 6.8 eV.

Answer: C

Question : Energy required for the electron excitation in Li++ from the first to the third Bohr orbit is
(a) 36.3 eV
(b) 108.8 eV
(c) 122.4 eV
(d) 12.1 eV

Answer: B

Question : The ratio of the energies of the hydrogen atom in its first to second excited states is
(a) 1/4
(b) 4/9
(c) 9/4
(d) 4

Answer: C

Question : Excitation energy of a hydrogen like ion in its excitation state is 40.8 eV. Energy needed to remove the electron from the ion in ground state is
(a) 54.4 eV
(b) 13.6 eV
(c) 40.8 eV
(d) 27.2 eV

Answer: A

Question : Suppose potential energy between electron and proton at separation r is given by U : K ln (r), where K is a constant. For such a hypothetical hydrogen atom, the ratio of energy difference between energy levels (n : 1 and n : 2) and (n : 2 and n : 4) is
(a) 1
(b) 2
(c) 3
(d) 4

Answer: A

Question : An unknown hot gas emits radiation of wavelengths 46.0 nm, 82.8 nm and 103.5 nm only. Assume that the atoms have only two excited states and the difference between consecutive energy levels decreases as energy is increased. Taking the energy of the highest energy state to be zero, find the energies of the ground state and the first excited state.
(a) –27 eV, – 12 eV
(b) –6 eV, – 3 eV
(c) –11 eV, – 8 eV
(d) –9 eV, – 3 eV

Answer: A