Title 24. Atomic Physics -2 Easy.pdf ✅

1. If in nature there may not be an element for which the principal quantum number n > 4, then the total possible number of elements will be (a) 60 (b) 32 (c) 4 (d) 64 2. In the Bohr's hydrogen atom model, the radius of the stationary orbit is directly proportional to (n = principle quantum number) (a) −1 n (b) n (c) −2 n (d) 2 n 3. In the n th orbit, the energy of an electron eV n En 2 13.6 = − for hydrogen atom. The energy required to take the electron from first orbit to second orbit will be (a) 10.2 eV (b) 12.1 eV (c) 13.6 eV (d) 3.4 eV 4. In the following atoms and moleculates for the transition from n= 2 to n = 1, the spectral line of minimum wavelength will be produced by (a) Hydrogen atom (b) Deuterium atom (c) Uni-ionized helium (d) di-ionized lithium 5. The Lyman series of hydrogen spectrum lies in the region (a) Infrared (b) Visible (c) Ultraviolet (d) Of X − rays 6. The size of an atom is of the order of (a) m 8 10 − (b) m 10 10 − (c) m 12 10 − (d) m 14 10 − 7. Which one of the series of hydrogen spectrum is in the visible region (a) Lyman series (b) Balmer series (c) Paschen series (d) Bracket series 8. The energy levels of the hydrogen spectrum is shown in figure. There are some transitions A, B, C, D and E. Transition A, B and C respectively represent (a) First member of Lyman series, third spectral line of Balmer series and the second spectral line of Paschen series (b) Ionization potential of hydrogen, second spectral line of Balmer series and third spectral line of Paschen series (c) Series limit of Lyman series, third spectral line of Balmer series and second spectral line of Paschen series (d) Series limit of Lyman series, second spectral line of Balmer series and third spectral line of Paschen series 9. In the above figure D and E respectively represent (a) Absorption line of Balmer series and the ionization potential of hydrogen (b) Absorption line of Balmer series and the wavelength lesser than lowest of the Lyman series (c) Spectral line of Balmer series and the maximum wavelength of Lyman series (d) Spectral line of Lyman series and the absorption of greater wavelength of limiting value of Paschen series 10. The Rutherford -particle experiment shows that most of the -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 11. Which of the following is true (a) Lyman series is a continuous spectrum (b) Paschen series is a line spectrum in the infrared (c) Balmer series is a line spectrum in the ultraviolet (d) The spectral series formula can be derived from the Rutherford model of the hydrogen atom 12. The energy required to knock out the electron in the third orbit of a hydrogen atom is equal to (a) 13.6 eV (b) eV 9 13.6 + (c) eV 3 13.6 − (d) eV 13.6 3 − 13. An electron has a mass of kg 31 9.1 10 −  . It revolves round the nucleus in a circular orbit of radius metre 10 0.529 10 −  at a speed of 2.2 10 m /s 6  . The magnitude of its linear momentum in this motion is (a) 1.1 10 kg m /s 34  − − (b) 2.0 10 kg m / s 24  − − (c) 4.0 10 kg m / s 24  − − (d) 4.0 10 kg m / s 31  − − n= n=6 n=5 n=4 n=3 n=2 n=1 – 0.00 eV – 0.36 eV – 0.54 eV – 0.85 eV – 1.51 eV – 3.39 eV – 13.5 eV A B C D E
14. In a beryllium atom, if a0 be the radius of the first orbit, then the radius of the second orbit will be in general (a) 0 na (b) 0 a (c) 0 2 n a (d) 2 0 n a 15. The ionization potential for second He electron is (a) 13.6 eV (b) 27.2 eV (c) 54.4 eV (d) 100 eV 16. The energy required to remove an electron in a hydrogen atom from n = 10 state is (a) 13.6 eV (b) 1.36 eV (c) 0.136 eV (d) 0.0136 eV 17. Every series of hydrogen spectrum has an upper and lower limit in wavelength. The spectral series which has an upper limit of wavelength equal to 18752 Å is (a) Balmer series (b) Lyman series (c) Paschen series (d) Pfund series (Rydberg constant 7 R = 1.097 10 per metre) 18. The kinetic energy of the electron in an orbit of radius r in hydrogen atom is (e = electronic charge) (a) 2 2 r e (b) r e 2 2 (c) r e 2 (d) 2 2 2r e 19. Ionization potential of hydrogen atom is 13.6 V. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV. The spectral lines emitted by hydrogen atoms according to Bohr's theory will be (a) One (b) Two (c) Three (d) Four 20. Energy levels A, B, C of a certain atom corresponding to increasing values of energy i.e. EA  EB  EC . If 1 2 3  ,  ,  are the wavelengths of radiations corresponding to the transitions C to B, B to A and C to A respectively, which of the following statements is correct (a) 3 = 1 + 2 (b) 1 2 1 2 3      + = (c) 1 + 2 + 3 = 0 (d) 2 2 2 1 2 3 =  +  21. The angular momentum of electron in n th orbit is given by (a) nh (b) n h 2 (c) 2 h n (d) 2 2 h n 22. The ratio of the energies of the hydrogen atom in its first to second excited state is (a) 1/ 4 (b) 4/9 (c) 9/ 4 (d) 4 23. An electron jumps from the 4th orbit to the 2nd orbit of hydrogen atom. Given the Rydberg's constant 5 1 10 − R = cm . The frequency in Hz of the emitted radiation will be (a) 5 10 16 3  (b) 15 10 16 3  (c) 15 10 16 9  (d) 15 10 4 3  24. The ionisation potential of hydrogen atom is 13.6 volt. The energy required to remove an electron in the n = 2 state of the hydrogen atom is (a) 27.2 eV (b) 13.6 eV (c) 6.8 eV (d) 3.4 eV 25. The ionisation energy of 10 times ionised sodium atom is (a) 13.6 eV (b) 13.6 11 eV (c) eV 11 13.6 (d) eV 2 13.6 (11) 26. If the wavelength of the first line of the Balmer series of hydrogen is 6561 Å , the wavelength of the second line of the series should be (a) 13122 Å (b) 3280 Å (c) 4860 Å (d) 2187 Å 27. The following diagram indicates the energy levels of a certain atom when the system moves from 2E level to E, a photon of wavelength  is emitted. The wavelength of photon produced during its transition from 3 4 E level to E is 1 2 3 C B A 2E 4/3E E
(a)  / 3 (b) 3 / 4 (c) 4 / 3 (d) 3 28. A beam of fast moving alpha particles were directed towards a thin film of gold. The parts A , B and C of the transmitted and reflected beams corresponding to the incident parts A, B and C of the beam, are shown in the adjoining diagram. The number of alpha particles in (a) B will be minimum and in C maximum (b) A will be maximum and in B minimum (c) A will be minimum and in B maximum (d) C will be minimum and in B maximum 29. According to Bohr's theory the radius of electron in an orbit described by principal quantum number n and atomic number Z is proportional to (a) 2 2 Z n (b) 2 2 n Z (c) n Z 2 (d) Z n 2 30. The radius of electron's second stationary orbit in Bohr's atom is R. The radius of the third orbit will be (a) 3 R (b) 2.25 R (c) 9 R (d) 3 R 31. If m is mass of electron, v its velocity, r the radius of stationary circular orbit around a nucleus with charge Ze, then from Bohr's first postulate, the kinetic energy 2 2 1 K = mv of the electron in C.G.S. system is equal to (a) r Ze 2 2 1 (b) 2 2 2 1 r Ze (c) r Ze 2 (d) 2 r Ze 32. Consider an electron in the n th orbit of a hydrogen atom in the Bohr model. The circumference of the orbit can be expressed in terms of the de Broglie wavelength  of that electron as (a) (0.259 ) n (b) n (c) (13.6)  (d) n 33. In any Bohr orbit of the hydrogen atom, the ratio of kinetic energy to potential energy of the electron is (a) 1/2 (b) 2 (c) −1 / 2 (d) – 2 34. The spectral series of the hydrogen spectrum that lies in the ultraviolet region is the (a) Balmer series (b) Pfund series (c) Paschen series (d) Lyman series 35. Figure shows the energy levels P, Q, R, S and G of an atom where G is the ground state. A red line in the emission spectrum of the atom can be obtained by an energy level change from Q to S. A blue line can be obtained by following energy level change (a) P to Q (b) Q to R (c) R to S (d) R to G 36. A hydrogen atom (ionisation potential 13.6 eV) makes a transition from third excited state to first excited state. The energy of the photon emitted in the process is (a) 1.89 eV (b) 2.55 eV (c) 12.09 eV (d) 12.75 eV 37. The figure indicates the energy level diagram of an atom and the origin of six spectral lines in emission (e.g. line no. 5 arises from the transition from level B to A). The following spectral lines will also occur in the absorption spectrum (a) 1, 4, 6 (b) 4, 5, 6 (c) 1, 2, 3 (d) 1, 2, 3, 4, 5, 6 38. When a hydrogen atom is raised from the ground state to an excited state (a) P.E. increases and K.E. decreases (b) P.E. decreases and K.E. increases (c) Both kinetic energy and potential energy increase B B A C C A P Q R S G 1 2 3 4 5 6 X A B C
(d) Both K.E. and P.E. decrease 39. An electron makes a transition from orbit n = 4 to the orbit n = 2 of a hydrogen atom. The wave number of the emitted radiations (R = Rydberg's constant) will be (a) 3R 16 (b) 16 2R (c) 16 3R (d) 16 4R 40. In Bohr model of the hydrogen atom, the lowest orbit corresponds to (a) Infinite energy (b) The maximum energy (c) The minimum energy (d) Zero energy 41. The ratio of the kinetic energy to the total energy of an electron in a Bohr orbit is (a) – 1 (b) 2 (c) 1 : 2 (d) None of these 42. An electron in the n = 1 orbit of hydrogen atom is bound by 13.6 eV. If a hydrogen atom is in the n = 3 state, how much energy is required to ionize it (a) 13.6 eV (b) 4.53 eV (c) 3.4 eV (d) 1.51 eV 43. Which of the following statements about the Bohr model of the hydrogen atom is false (a) Acceleration of electron in n = 2 orbit is less than that in n = 1 orbit (b) Angular momentum of electron in n = 2 orbit is more than that in n = 1 orbit (c) Kinetic energy of electron in n = 2 orbit is less than that in n = 1 orbit (d) Potential energy of electron in n = 2 orbit is less than that in n = 1 orbit 44. If an electron jumps from 1st orbital to 3rd orbital, then it will . (a) Absorb energy (b) Release energy (c) No gain of energy (d) None of these 45. The ratio of the frequencies of the long wavelength limits of Lyman and Balmer series of hydrogen spectrum is (a) 27 : 5 (b) 5 : 27 (c) 4 : 1 (d) 1 : 4 46. Which of the following transitions in a hydrogen atom emits photon of the highest frequency (a) n = 1 to n = 2 (b) n = 2 to n = 1 (c) n = 2 to n = 6 (d) n = 6 to n = 2 47. In terms of Rydberg's constant R, the wave number of the first Balmer line is (a) R (b) 3R (c) 36 5R (d) 9 8R 48. If the ionisation potential of helium atom is 24.6 volt, the energy required to ionise it will be (a) 24.6 eV (b) 24.6 V (c) 13.6 V (d) 13.6 eV 49. Which of the transitions in hydrogen atom emits a photon of lowest frequency (n = quantum number) (a) n = 2 to n = 1 (b) n = 4 to n = 3 (c) n = 3 to n = 1 (d) n = 4 to n = 2 50. According to Bohr's theory, the expressions for the kinetic and potential energy of an electron revolving in an orbit is given respectively by (a) r e 0 2 8 + and r e 0 2 4 − (b) r e 2 8 0 + and r e 2 0 4 − (c) r e 0 2 8 − and r e 0 2 4 − (d) r e 0 2 8 + and r e 0 2 4 + 51. In a hydrogen atom, which of the following electronic transitions would involve the maximum energy change (a) From n = 2 to n = 1 (b) From n = 3 to n = 1 (c) From n = 4 to n = 2 (d) From n = 3 to n = 2 52. In the lowest energy level of hydrogen atom, the electron has the angular momentum (a)  / h (b) h / (c) h / 2 (d) 2 / h 53. The minimum energy required to excite a hydrogen atom from its ground state is (a) 13.6 eV (b) −13.6 eV (c) 3.4 eV (d) 10.2 eV 54. Ratio of the wavelengths of first line of Lyman series and first line of Balmer series is (a) 1: 3 (b) 27 : 5 (c) 5 : 27 (d) 4 : 9 55. The Rydberg constant R for hydrogen is (a) 2 2 2 0 2 . 4 1 ch me R           = − (b) 2 2 4 0 2 . 4 1 ch me R           = (c) 2 2 2 4 2 0 2 . 4 1 c h me R           = (d) 3 2 4 2 0 2 . 4 1 ch me R           =