Title Atoms (ALL DPPs).pdf ✅

Atoms Part-04  Digital [1] 1. According to Bohr's theory the moment of momentum of an electron revolving in second orbit of hydrogen atom will be (1) 2h (2) h (3) h  (4) 2h  2. In Bohr's model of hydrogen atom, let PE represents potential energy and TE the total energy. In going to a higher level (1) PE decreases, TE increases (2) PE increases, TE increases (3) PE decreases, TE decreases (4) PE increases, TE decreases 3. Which of the following statements are true regarding Bohr's model of hydrogen atom (I) Orbiting speed of electron decreases as it shifts to discrete orbits away from the nucleus (II) Radii of allowed orbits of electron are proportional to the principal quantum number (III) Frequency with which electrons orbits around the nucleus in discrete orbits is inversely proportional to the principal quantum number (IV) Binding force with which the electron is bound to the nucleus increases as it shifts to outer orbits Select correct answer using the codes given below Codes : (1) I and III (2) II and IV (3) I, II and III (4) II, III and IV 4. Energy of electron in a orbit of H-atom is (1) Positive (2) Negative (3) Zero (4) Nothing can be said Bohr Model of Hydrogen Atom DPP-01 TG: @Chalnaayaaar
Atoms Part-04  Digital [2] 5. The concept of stationary orbits was proposed by (1) Neil Bohr (2) J.J. Thomson (3) Ruther ford (4) I. Newton 6. In hydrogen atom which quantity is integral multiple of h 2 (1) Angular momentum (2) Angular velocity (3) Angular acceleration (4) Momentum 7. Which of the following statement is true regarding Bohr's model of hydrogen atom? (i) Orbiting speed of electrons decreases as it falls to discrete orbits away from the nucleus. (ii) Radii of allowed orbits of electrons are proportional to the principal quantum number. (iii) Frequency with which electrons orbit around the nucleus in discrete orbits is inversely proportional to the principal quantum number. (iv) Binding force with which the electron is bound to the nucleus increases as it shifts to outer orbits. Select the correct answer using the codes given below : (1) i and iii (2) ii and iv (3) I, ii and iii (4) ii, iii and iv 8. Which of the following statements is true of hydrogen atom? (1) Angular momentum 1 n  (2) Linear momentum 1 n  (3) Radius 1 n  (4) Energy 1 n  9. Consider an electron in the nth 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 the (1) (0.259) n (2) n (3) (13.6)  (4) n TG: @Chalnaayaaar
Atoms Part-04  Digital [3] SOLUTIONS 1. (3) Angular momentum h L n 2   =      For this case n=2, hence h h L 2 2 =  =   2. (2) As n increases P.E. increases and K.E. decreases. 3. (1) Orbital speed varies inversely as the radius of the orbit. Energy increases with the increase in quantum number. 4. (2) n 2 13.6 E eV n = − 5. (1) 6. (1) 7. (1) In case of Bohr's model of hydrogen atom, orbital speed varies inversely as the radius of the orbit and energy increases with increase in quantum number. Further frequency = v 2 r Here 1 v n  and 2 r n  Frequency 1 n  8. (2) We know that angular momentum nh nh L mvr r mv 2 r 2 r = = = =   Answer key Question 1 2 3 4 5 6 7 8 9 Answer 3 2 1 2 1 1 1 2 4 TG: @Chalnaayaaar
Atoms Part-04  Digital [4] Now, 2 r n  2 nh mv P 2 n =   h P 2 n   and 1 P n  9. (4) According to Bohr's theory mvr = n h 2  Circumference h 2 r n n mv    = =      TG: @Chalnaayaaar