Class 12 Physics Chapter 12 Atoms MCQ Questions with Answers

Atoms Class 12 MCQ is one of the best strategies to prepare for the CBSE Class 12 Board exam. If you want to complete a grasp concept or work on one’s score, there is no method except constant practice. Students can improve their speed and accuracy by doing more MCQs on Atoms Class 12, which will help them all through their board test.

Atoms Class 12 MCQ Questions with Answers

Class 12 Physics MCQ with answers are given here to chapter the Atoms. These MCQs are based on the latest CBSE board syllabus and relate to the latest Class 12 Physics syllabus. By Solving these Class 12 MCQs, you will be able to analyze all of the concepts quickly in the chapter and get ready for the Class 12 Annual exam.

Learn Class 12 Atoms MCQ with answers pdf free download according to the latest CBSE and NCERT syllabus. Students should prepare for the examination by solving CBSE Class 12 Atoms MCQ with answers given below.

Question 1. An alpha nucleus of energy 1/2 mv2 bombards a heavy nuclear target of charge Ze. Then the distance of closest approach for the alpha nucleus will be proportional to
(a) 1/Ze
(b) v2
(c) 1/m
(d) 1/v4

Question 2. When an a-particle of mass m moving with velocity v bombards on a heavy nucleus of charge Ze, its distance of closest approach from the nucleus depends on m as
(a) 1/m²
(b) m
(c) 1/m
(d) 1/√m

Question 3. In a Rutherford scattering experiment when a projectile of charge z1 and mass M1 approaches a target nucleus of charge z2 and mass M2, the distance of closest approach is r0. The energy of the projectile is
(a) directly proportional to z1z2
(b) inversely proportional to z1
(c) directly proportional to mass M₁
(d) directly proportional to M₁ × M₂

Question 4. The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is
(a) 1
(b) 4
(c) 0.5
(d) 2

Question 5. Ratio of longest wavelengths corresponding to Lyman and Balmer series in hydrogen spectrum is
(a) 7/29
(b) 9/31
(c) 5/27
(d) 5/23

Question 6. Given the value of Rydberg constant is 10⁷ m^–1, the wave number of the last line of the Balmer series in hydrogen spectrum will be
(a) 0.25 × 10⁷ m^–1
(b) 2.5 × 10⁷ m^–1
(c) 0.025 × 10⁴ m^–1
(d) 0.5 × 10⁷ m^–1

Question 7. The wavelength of the first line of Lyman series for hydrogen atom is equal to that of the second line of Balmer series for a hydrogen like ion. The atomic number Z of hydrogen like ion is
(a) 3
(b) 4
(c) 1
(d) 2 

Question 8. Which source is associated with a line emission spectrum?
(a) Electric fire
(b) Neon street sign
(c) Red traffic light
(d) Sun

Question 9. The total energy of an electron in an atom in an orbit is – 3.4 eV. Its kinetic and potential energies are, respectively
(a) 3.4 eV, 3.4 eV
(b) – 3.4 eV, – 3.4 eV
(c) – 3.4 eV, – 6.8 eV
(d) 3.4 eV, – 6.8 eV

Question 10. The radius of the first permitted Bohr orbit for the electron, in a hydrogen atom equals 0.51 Å and its ground state energy equals –13.6 eV. If the electron in the hydrogen atom is replaced by muon (m–) [charge same as electron and mass 207 me], the first Bohr radius and ground state energy will be
(a) 0.53 × 10^–13 m, –3.6 eV
(b) 25.6 × 10^–13 m, –2.8 eV
(c) 2.56 × 10^–13 m, –2.8 keV
(d) 2.56 × 10^–13 m, –13.6 eV 

Question 11. For which one of the following, Bohr model is not valid?
(a) Hydrogen atom
(b) Singly ionised helium atom (He+)
(c) Deuteron atom
(d) Singly ionised neon atom (Ne+) 

Question 12. The ratio of kinetic energy to the total energy of an electron in a Bohr orbit of the hydrogen atom, is
(a) 1 : 1
(b) 1 : –1
(c) 2 : –1
(d) 1 : –2 

Question 13. An electron in hydrogen atom makes a transition n₁ → n₂ where n1 and n2 are principal quantum numbers of the two states. Assuming Bohr’s model to be valid, the time period of the electron in the initial state is eight times that in the final state. The possible values of n1 and n2 are
(a) n₁ = 6 and n₂ = 2
(b) n₁ = 8 and n₂ = 1
(c) n₁ = 8 and n₂ = 2
(d) n₁ = 4 and n₂ = 2

Question 14. Monochromatic radiation emitted when electron on hydrogen atom jumps from first excited to the ground state irradiates a photosensitive material.
The stopping potential is measured to be 3.57 V. The threshold frequency of the material is
(a) 4 × 10¹⁵ Hz
(b) 5 × 10¹⁵ Hz
(c) 1.6 × 10¹⁵ Hz
(d) 2.5 × 10¹⁵ Hz 

Question 15. Consider 3rd orbit of He+ (Helium), using non-relativistic approach, the speed of electron in this orbit will be [given K = 9 × 109 constant, Z = 2 and h (Planck’s constant) = 6.6 × 10^–34 J s]
(a) 0.73 × 10⁶ m/s
(b) 3.0 × 10⁸ m/s
(c) 2.92 × 10⁶ m/s
(d) 1.46 × 10⁶ m/s

Question 16. An electron in the hydrogen atom jumps from excited state n to the ground state. The wavelength so emitted illuminates a photosensitive material having work function 2.75 eV. If the stopping potential of the photoelectron is 10 V, then the value of n is
(a) 2
(b) 3
(c) 4
(d) 5 

Question 17. The ionization energy of Li⁺⁺ is equal to
(a) 9hcR
(b) 6hcR
(c) 2hcR
(d) hcR.

Question 18. The Rutherford a-particle experiment shows that most of the a-particles pass through almost unscattered while some are scattered through large angles. What information does it give about the structure of the atom?
(a) Atom is hollow.
(b) The whole mass of the atom is concentrated in a small centre called nucleus
(c) Nucleus is positively charged
(d) All the above

Question 19. 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) 0.65 eV
(b) 1.9 eV
(c) 11.1 eV
(d) 13.6 eV 

Question 20. The energy of a hydrogen atom in the ground state is –13.6 eV. The energy of a He+ ion in the first excited state will be
(a) –13.6 eV
(b) –27.2 eV
(c) –54.4 eV
(d) –6.8 eV 

Question 21. The electron in the hydrogen atom jumps from excited state (n = 3) to its ground state (n = 1) and the photons thus emitted irradiate a photosensitive material. If the work function of the material is 5.1 eV, the stopping potential is estimated to be (the energy of the electron in nth state En = −13.6/ n². eV )
(a) 5.1 V
(b) 12.1 V
(c) 17.2 V
(d) 7 V 

Question 22. The total energy of electron in the ground state of hydrogen atom is –13.6 eV. The kinetic energy of an electron in the first excited state is
(a) 6.8 eV
(b) 13.6 eV
(c) 1.7 eV
(d) 3.4 eV 

Question 23. The total energy of an electron in the first excited state of hydrogen atom is about –3.4 eV. Its kinetic energy in this state is
(a) 3.4 eV
(b) 6.8 eV
(c) –3.4 eV
(d) –6.8 eV

Question 24. The ground state energy of hydrogen atom is –13.6 eV. When its electron is in the first excited state, its excitation energy is
(a) 10.2 eV
(b) 0
(c) 3.4 eV
(d) 6.8 eV 

Question 25. In which of the following systems will the radius of the first orbit (n = 1) be minimum?
(a) doubly ionized lithium
(b) singly ionized helium
(c) deuterium atom
(d) hydrogen atom

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Question 26. The third line of Balmer series of an ion equivalnet to hydrogen atom has wavelength of 108.5 nm. The ground state energy of an electron of this ion will be
(a) 3.4 eV
(b) 13.6 eV
(c) 54.4 eV
(d) 122.4 eV

Question 27. The Bohr model of atoms
(a) Assumes that the angular momentum of electrons is quantized.
(b) Uses Einstein’s photoelectric equation.
(c) Predicts continuous emission spectra for atoms.
(d) Predicts the same emission spectra for all types of atoms. 

Question 28. The first line of Balmer series has wavelength 6563 Å. What will be the wavelength of the first member of Lyman series
(a) 1215.4 Å
(b) 2500 Å
(c) 7500 Å
(d) 600 Å

Question 29. The life span of atomic hydrogen is
(a) fraction of one second
(b) one year
(c) one hour
(d) one day

Question 30. The energy of hydrogen atom in nth orbit is En then the energy in nth orbit of singly ionised helium atom will be
(a) 4En
(b) En/4
(c) 2En
(d) En/2 

Question 31. The energy of the ground electronic state of hydrogen atom is –13.6 eV. The energy of the first excited state will be
(a) –27.2 eV
(b) –52.4 eV
(c) –3.4 eV
(d) –6.8 eV

Question 32. According to Bohr’s principle, the relation between principal quantum number (n) and radius of orbit (r) is
(a) r ∝ 1/n
(b) r ∝ 1/n²
(c) r ∝ n
(d) r ∝ n₂ 

Question 33. When hydrogen atom is in its first excited level, its radius is ………. of the Bohr radius.
(a) twice
(b) 4 times
(c) same
(d) half 

Question 34. In a Rutherford experiment, the number of particles scattered at 90° angle are 28 per minute then number of scattered particles at an angle 60° and 120° will be
(a) 117 per minute, 25 per minute
(b) 50 per minute, 12.5 per minute
(c) 100 per minute, 200 per minute
(d) 112 per minute, 12.4 per minute

Question 35. When a hydrogen atom is raised from the ground state to an excited state,
(a) both K.E. and P.E. increase
(b) both K.E. and P.E. decrease
(c) the P.E. decreases and K.E. increases
(d) the P.E. increases and K.E. decreases. 

Question 36. In Hydrogen spectrum, the wavelength of H_a line is 656 nm, whereas in the spectrum of a distant galaxy, H_a line wavelength is 706 nm. Estimated speed of the galaxy with respect to earth is
(a) 2 × 10⁸ m/s
(b) 2 × 10⁷m/s
(c) 2 × 10⁶ m/s
(d) 2 × 10⁵ m/s

Question 37. In terms of Bohr radius a0, the radius of the second Bohr orbit of a hydrogen atom is given by
(a) 4a0
(b) 8a0
(c) 2a0
(d) 2a0 

Question 38. The ground state energy of H-atom is –13.6 eV. The energy needed to ionize H-atom from its second excited state
(a) 1.51 eV
(b) 3.4 eV
(c) 13.6 eV
(d) none of these 

Question 39. 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 

Question 40. To explain his theory, Bohr used
(a) conservation of linear momentum
(b) quantisation of angular momentum
(c) conservation of quantum frequency
(d) none of these

Question 41. The ionisation potential of H-atom is 13.6 V. When it is excited from ground state by monochromatic radiations of 970.6 Å, the number of emission lines will be (according to Bohr’s theory)
(a) 10
(b) 8
(c) 6
(d) 4

Question 42. The ionisation energy of hydrogen atom is 13.6 eV,the ionisation energy of a singly ionised helium atom would be
(a) 13.6 eV
(b) 27.2 eV
(c) 6.8 eV
(d) 54.4 eV

Question 43. 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

Question 44. If an electron in a hydrogen atom jumps from the 3rd orbit to the 2nd orbit, it emits a photon of wavelength l. When it jumps from the 4th orbit to the 3rd orbit, the corresponding wavelength of the photon will be
(a) 16/25λ
(b) 9/16λ
(c) 20/7λ
(d) 20/13λ

Question 45. Hydrogen atom in ground state is excited by a monochromatic radiation of l = 975 Å. Number of spectral lines in the resulting spectrum emitted will be
(a) 3
(b) 2
(c) 6
(d) 10 

Question 46. An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be
(a) 24hR/25m
(b) 25hR/24m
(c) 25m/24hR
(d) 24m/25hR
(m is the mass of the electron, R Rydberg constant and h Planck’s constant)

Question 47. Electron in hydrogen atom first jumps from third excited state to second excited state and then from second excited to the first excited state. The ratio of the wavelengths l1 : l2 emitted in the two cases is
(a) 7/5
(b) 27/20
(c) 27/5
(d) 20/7 

Question 48. The transition from the state n = 3 to n = 1 in a hydrogen like atom results in ultraviolet radiation.
Infrared radiation will be obtained in the transition from
(a) 2 → 1
(b) 3 → 2
(c) 4 → 2
(d) 4 → 3 

Question 49. Taking Rydberg’s constant R_H = 1.097 × 10⁷m, first and second wavelength of Balmer series in hydrogen spectrum is
(a) 2000 Å, 3000 Å
(b) 1575 Å, 2960 Å
(c) 6529 Å, 4280 Å
(d) 6552 Å, 4863 Å

Question 50. A hydrogen atom in its ground state absorbs 10.2 eV of energy. The orbital angular momentum is increased by
(a) 1.05 × 10^–34 J-s
(b) 3.16 × 10^–34 J-s
(c) 2.11 × 10^–34 J-s
(d) 4.22 × 10^–34 J-s

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