NCERT Class XI chapter 2 Structure of atom practice exercise

1. ATOMICSTRUCTURE
NODE AND NODAL PLANE
Node is defined as a region where the probability of finding an electron is zero.
The planes passing through the angular nodal points are called nodal planes.
Nodes
No. of radial or spherical nodes = n –  – 1
No. of angular nodes =  , Total no. of nodes = n–1
KEY CONCEPTS
1. According to Dalton’s atomic theory atom is considered as smallest indivisible parcticle of matter.
Electron, proton and neutron are the subatomic particles.
2. According to Rutherford model, atom consist of nucleus. The positive charge and the mass of the
atom is concentrated in the nucleus. The electrons revolve round the nucleus in circular paths.
3. According to planck’s quantum theory enegy is emitted or absorbed discontinuously in the form of
quanta. Quantum of visible light called photons.
4. Energy of one quantum = h
5. According to Bohr’s theory electron revolve round the nucleus only in those orbit where its angular
momentum is an integral multiple of
2
h

.
6.
2
h
mvr n

 and  E h
7. Important formulation derived from Bohr’s atomic model.
(i) Radius (r) =
2 2 2
0
2 2
0.529
4
n h n
A
mkZe Z
 
(ii) Energy (E) of electron in nth orbit =
2 2 4 2 2
2 2 2
2 mZ e K Z
13.6 eV
n h n

    
Energy (E) of electron in nth orbit =
2
18
2
2.18 10 /

z
J atom
n
(iii) Velocity of electron in nth orbit (v) =
8
2.18 10 / sec.
Z
cm
n
 
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Structure of Atom

2. ATOMICSTRUCTURE CHEMISTRY
(iv) Number of revolutions per second by an electron in nth orbit =
2
V
r
(v) Number of revolutions per second by an electron in nth orbit =
2 4
2 3 3
02
Z me
n h


(vi) Frequency of electron in the nth orbit =
2
15
3
6.62 10
Z
n
 
8. Bohr’s theory of atom is applicable to only Hydrogen like species
9.
2
H 2 2
1 2
1 1 1
R Z ;
n n
 
     
   HR = Rydberg’s constant
10. Maximum number of lines produced when electron returns from nth
orbit to ground state =
n(n-1)/2
11. According to de-Broglie matter has particle as well as wave nature.
 
h h
p mV

2
h
Em
  Where E is KE of the parcticle
12. According to Heisenberg’s uncertainity principle .
4
h
x p

  
13. Principal quantum number (n) = 1,2,3,……
14. Azimuthal quantum number (  ) = 0, 1, 2 … n 1
15. Magnetic quantum number  m to   
16. Spin quantum number (s)
1 1
and
2 2
  
17. Orbital angular momentum    
h
1 1 h
2
  

   
18. Number of subshell in a shell = n
19. Number of maximum orbitals in a shell = 2
n
20. Number of maximum orbitals in a subshell = 2 1
21. No of radial nodes n 1  
22. No of angular nodes = 
CONCEPTUAL QUESTIONS
1. Whichofthefollowingarrangementoftwoelectronsintwodegeneratedorbitalsisnotpossibleat
all
(A) (B) (C) (D) all ofthese
2. Difference between nth
and (n + 1)th
Bohr’s radius of H atom is equal to it’s (n – 1)th
Bohr’s
radius. Thevalueofnis
(A)1 (B) 2 (C) 3 (D) 4
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3. ATOMICSTRUCTURE CHEMISTRY
3. AccordingtoSchrödingermodel nature ofelectron in an atomis as
(A)particlesonly (B) waveonly
(C)bothsimultaneously (D) sometimes waveandsometimesparticle
4. IfRH
istheRydbergconstantforhydrogenatoms,theratioof v ofserieslimitsofBalmerseriesof
hydrogenand Li2+
is
(A) HR
9
(B) H9R
4
(C) 9 (D)
1
9
5. Spin ofelectronis
(A)rotationofelectronabout it’s ownaxis
(B) clockwiseandanticlockwiserotationofelectron
(C)a quantum number which depends upondirection and speed ofrotation of electron
(D)anintrinsiccharacteristicofelectronconnectedwithitsmagneticfield
6. Theratiooforbitalangularmomentumandspinangularmomentumofanelectronin‘p’orbitalis
(A)
3
2
(B)
3
2
(C)
2 2
3
(D)
2
3
7. Probabilityof findingtheelectron 2
ψ of‘s’ orbital does notdepend upon
(A)distancefromthenucleus (r) (B) energyof‘s’orbital
(C)principalquantumnumber (D) azimuthalquantumnumber
8. IfHund’s ruleis applicable,p3
configurationis becauseinthis arrangement
(A)electrostaticrepulsionisminimum
(B) magneticattractionwithoutermagnaticfieldismaximum
(C)halffilledismorestable
(D)all ofthese
9. Theuncertaintyinthemomentum of a particle is3.3 ×10–2
kgms–1
. Calculatetheuncertaintyin
itsposition.
(A)1.6 × 10–33
m (B) 1.6 × 10–32
m (C) 16 × 10–30
m (D) 1.6 × 10–30
m
10. Whichofthefollowingcannotchangeitsmagneticmomentonexcitation?
(A)H (B) Be (C) B (D) O
11. Electron and protonareaccelerated through onevolt of potential difference,theratio oftheir
wavelengths isequalto
(A)
p
e
m
m
(B)
p e
e p
m v
m v (C)
2
p
2
e
m
m
(D)
p
e
m
m
12. 1 moleofHe+
ionisexcited.Spectral analysis showedtheexistenceof50%ions in3rd
level,25%
in 2nd
level andremaining25%ingroundstate.The totalenergyevolvedwhen alltheions return
to groundstate is
(A)232.88 × 104
J (B) 331.13 × 104
J (C) 58.22 × 104
J (D) 660 × 104
J
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4. ATOMICSTRUCTURE CHEMISTRY
13. -particles of6MeVenergyisscatteredbackfrom asilverfoil.Calculatethemaximum volume
in which the entire charge of the atom is supposed to be concentrated? [Zfor silver = 47]
(A)3.6 × 10–28
m3
(B) 5.97 × 10–42
m3
(C) 6.55 × 10–71
m3
(D) 48 × 10–42
m3
14. When a certain metal was irradiated with a light of 8.1 × 1016
Hz frequency, the photoelectron
emitted had1.5 times the kineticenergyas the photoelectrons emitted when the samemetal was
irradiatedwithlight5.8×1016
Hzfrequency.Ifthesamemetalis irradiatedwithlightof3.846nm
wavelength,what will betheenergyofthephotoelectronemitted?
(A)1.8 × 102
eV (B) 3.65 × 10–17
J (C) 2.28 × 102
eV (D) 4.37 × 10–17
J
15. What is the degeneracyof the level of the hydrogen atom that has the energy HR
.
9
 
 
 
(A)3 (B) 9 (C) 18 (D) 6
SINGLE CORRECT ANSWER TYPE
LEVEL - I
Subatomic particles
1. The increasing order (lowest first) for the values of e/m (charge/mass) for electron (e), proton (p),
neutron (n) and alpha particle (  ) is
(A)e, p, n,  (B)n, p, e,  (C)n, p,  , e (D)n,  , p, e
2. The ratio of charge and mass would be greater for
(A) Proton (B) Electron (C) Neutron (D) Alpha
3. Calcium (Ca) has atomic number 20 and mass number 40. Which of the following statements is not
correct about Ca atom?
(A) The number of protons is same as the number of neutrons
(B) The number of electrons is same as the number of neutrons
(C) The number of protons is half of the number of neutrons
(D) The number of nucleons is double the number of neutrons.
4. The triad of nuclei that is isotonic is
(A)14 15 17
6 7 9C, N, F (B)12 14 19
6 7 9C, N, F
(C)14 14 17
6 7 9C, N, F (D)14 14 19
6 7 9C, N, F
Atomic model
5. For the hydrogen atom, the energy of the electron is defined by the factor   2
nE 13.58/n eV
Here n is positive integer. The minimum quantity of energy which it can absorb in its primitive stage
is:
(A)1.00 eV (B)3.39 eV (C)6.79 eV (D)10.19 eV
6. The radius of Bohr’s first orbit is hydrogen atom is 0.053 nm. The radius of second orbit in
He+
could be
(A)0.0265 nm (B)0.0530 nm (C).106 nm (D)0.2120 nm
7. For which of the species, Bohr’s theory is not applicable ?
(A) Be+3
(B) Li+2
(C) He+2
(D) H
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5. ATOMICSTRUCTURE CHEMISTRY
8. Which of the following postulates does not belong to Bohr’s model of the atom?
(A)Angular momentum is an integral multiple of
h
2
(B) The electron stationed in the orbit is stable
(C) The path of an electron is circular
(D) The change in the energy levels of electron is continuous
9. In which orbit of the hydrogen atom is the speed of the electron is maximum?
(A) n = 2 (B) n = 1 (C) n = 3 (D) n = 4
10. For an electron, the product vn (velocity  principal quantum number) will be independent of the
(A) principal quantum number (B) velocity of the electron
(C) energy of the electron (D) frequency of its revolution
11. Assume that the potential energy of a hydrogen atom in its ground state is zero. Then its energy in the
first excited state will be
(A) 13.6 eV (B) 27.2 eV (C) 23.8eV (D) 10.2 eV
12. In an atom two electrons move around the nucleus in circular orbits of radii R and 4R. The ratio of the
time taken by them to complete one revolution is:
(A)1 : 4 (B)4 : 1 (C)1 : 8 (D) 8 : 7
13. Rutherford’s experiment on scattering of -particles showed for the first time that the atom has
(A)electrons (B)protons (C)nucleus (D)neutrons
14. The value of Bohr radius of hydrogen atom is
(A) 0.529 10-8
cm (B) 0.529  10-10
cm
(C) 0.529 10-12
cm (D) 0.529  10-6
cm
15. Ratio of radii of second and first Bohr orbits of H-atom
(A) 2 (B) 4 (C) 3 (D) 5
16. The radius of which of the following orbit is same as that of the first Bohr’s orbit of hydrogen atom
(A) He+
(n = 2) (B) Li+2
(n = 2) (C) Li2+
(n = 3) (D) Be3+
(n = 2)
17. Of the following transitions in hydrogen atom, the one which gives an absorption line of maximum
wavelength is
(A)n = 1 to n = 2 (B)n = 3 to n = 8 (C)n = 2 to n = 1 (D)n = 8 to n = 3
Atomic spectrum
18. The wavelength of a spectral line for an electronic transition is inversely related to
(A) The number of electrons undergoing the transition
(B) The nuclear charge of the atom
(C) The difference in the energy of the energy levels involved in the transition
(D) The velocity of electron undergoing the transition.
19. When the electron of a hydrogen atom jumps from the n = 4 to the n = 1 state, the number of spectral
lines emitted is
(A) 15 (B) 6 (C) 3 (D) 4
20. Electromagnetic radiation with maximum wavelength is:
(A)ultraviolet (B)radiowave (C)X-ray (D)Infrared
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6. ATOMICSTRUCTURE CHEMISTRY
21. The wave number of the first line in the Balmer series of hydrogen atom is 15200 cm–1
. What is the
wave number of the first line in the Balmer series of Be3+
?
(A) 2.432  105
cm–1
(B) 15200 cm–1
(C) 4  15200 cm–1
(D) 2  15200 cm–1
Photoelectric effect
22. When the frequency of light incident on a metallic plate is doubled, the KE of the emitted
photoelectron will be;
(A) doubled
(B) Halved
(C) Increased but more than doubled of the previous KE
(D)Remains unchanged Quantum number
Dual character
23. If the following matter waves travel with equal velocity, the longest wavelength is that of a/an.
(A)electron (B)proton (C)neutron (D)particle
24. If the velocity of hydrogen molecule is 5  104
cm sec-1
, then its de-Broglie wavelength is
(A) 2 Å (B) 4 Å (C) 8Å (D) 100 Å
Quantum Number
25. The correct set of four quantum number for the outermost electrons of rubidium (z = 37) is
(A) 5,0, 0, +
1
2
(B) 5, 1, 0, +
1
2
(C) 5, 1, 1, +
1
2
(D)6, 0, 0, +
1
2
26. The number of electrons in sulphur atom having n 3 
(A) 2 (B) 4 (C) 6 (D) 8
27. The orbital angular momentum of an electron in 2s-orbital is
(A) h/4p (B) zero (C) h/2p (D) 2h / 2
28. The quantum numbers of most energetic electron in Ar atom when it is in first excited state is
(A)2, 1, 0,  1/2 (B)4, 1, 1,  ½ (C)4, 0, 0,  1/2 (D)4, 1, 0,  1/2.
Electronic configuration of elements
29. Magnetic moments of V(Z = 23), Cr(Z = 24), Mn(Z = 25) are x, y, z. Hence:
(A) x = y = z (B) x < y < z (C) x < z < y (D) z < y < x
30. The outermost electronic configuration of the most electronegative element is
(A)ns2
np3
(B)ns2
np4
(C)ns2
np5
(D)ns2
np6
LEVEL - II
Subatomic Particle
31. The ratio of the e/m values of a proton and an  -particle is
(A)2 : 1 (B) 1 : 1 (C)1 : 2 (D) 1 : 4
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7. ATOMICSTRUCTURE CHEMISTRY
Atomic model
32. The energy of the second Bohr orbit in the hydrogen atom is –3.41eV. the energy of the second Bohr
orbit of He ion would be
(A)–0.85 eV (B)–13.64 eV (C)–1.70 eV (D)–6.82 eV
33. The ratio of energy of the electron in ground state of hydrogen to the electron in first excited state of
Be+3
is
(A)4 : 1 (B)1 : 4 (C)1 : 8 (D)8 : 1
34. The ratio of the difference in energy of electron between the first and second Bohr’s orbit to that
between second and third Bohr’s orbit is;
(A)
1
3
(B)
27
5
(C)
9
4
(D)
4
9
35. The difference in angular momentum associated with the electron in two successive orbits of hydrogen
atoms is
(A) h /  (B)h / 2 (C) h/2 (D)(n 1)h / 2 
36. The shortest  for the Lyman series of hydrogen atom is …… (Given 1
HR 109678 cm
 )
(A) 911.7Å (B)700Å (C) 600Å (D) 811Å
37. The velocity of an electron in the first Bohr orbit of a hydrogen atom is 6 1
2.19 10 ms
 . Its velocity
in the second orbit would be
(A) 6 1
1.10 10 ms
 (B) 6 1
4.38 l0 ms

(C) 5 1
5.5 10 ms
 (D) 6 1
8.76 10 ms

38. The ionization energy of a hydrogen atom in terms of Rydberg constant (RH
) is given by the expression
(A) RH
hc (B)RH
c (C) 2RH
hc (D)RH
hcNA
39. The ratio of the energies of photons of 2000Å to that of 4000Å is
(A) 2 (B) 4 (C)
1
2
(D)
1
4
40. The energy of an electron in the first Bohr orbit of H-atom is –13.6eV. The possible energy value of
the excited state in the Bohr orbit of H-atom is
(A) –4.2 eV (B) –3.4 eV (C) –6.8 eV (D) +6.8 eV
41. If 10–17
J of light energy is needed by the interior of human eye to see an object. The photons of green
light ( 550nm  ) needed to see the object are
(A)27 (B)28 (C)29 (D)30
42. The energy of a photon having wavelength 700 nm is
(A) 1.77 eV (B) 2.47 eV (C) 700 eV (D) 3.57 eV
43. A 1-kW radio transmitter operates at a frequency of 880 Hz. How many photons per second does it
emit?
(A) 1.71  1021
(B) 1.71  1030
(C)6.02  1023
(D) 2.85  1026
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8. ATOMICSTRUCTURE CHEMISTRY
44. The energy needed to excite a hydrogen atom from its ground state to its third excited state is
(A)12.1 eV (B) 10.2 eV (C)0.85 eV (D) 12.75 eV
Atomic spectrum
45. The first emission line in the atomic spectrum of hydrogen in the Balmer Series appears at
(A)
–1H9R
cm
400
(B)
–1H7R
cm
144
(C)
–1H3R
cm
4
(D)
–1H5R
cm
36
.
46. What element has a H-like spectrum, whose lines have wavelengths four times shorter than those of
atomic hydrogen?
(A)He (B)He+
(C)H (D)Li+2
47. The second line of Lyman series of H coincides with the 6th
line of Paschen series of an Ionic species
X. Find X assuming R to be same for both H and X?
(A)He+
(B)Li+2
(C)Li+
(D)H
48. The fourth line of the Balmer series corresponds to electron transition between energy levels
(A) 6 and 2 (B) 5 and 2 (C) 4 and 1 (D) 5 and 1
49. The ionization potential of hydrogen atom is 13.6 eV. The ionization potential of Be3+
ion is
(A) 217.6eV (B)109.8eV (C) 54.4 eV (D)136.0 eV
50. The wavelength of the third line of the Balmer series for a hydrogen atom is
(A)
H
21
100R (B)
H
100
21R (C)
H21R
100
(D)
H100R
21
Dual Character
51. Which particle among the following will have the smallest de Broglie wavelength, assuming that they
have the same velocity?
(A)A positron (B)A photon (C)An  -particle (D) A neutron
Photoelectric effect
52. The work function for a metal is 4 ev. To emit a photo electron of zero velocity from the surface of
the metal, the wavelength of incident light should be;
(A)2700Å (B)1700Å (C)5900Å (D)3100Å
Dual character
53. If 1 and 2 denote the de-Broglie wavelength of two particles with same masses but charges in
the ratio of 1 : 2 after they are accelerated from rest through the same potential difference, then
(A) 1 2   (B) 1 2   (C) 1 2   (D) 1 2  .
54. The velocity of electron of H-atom in its ground state is 6
2.2 10 m / s . The de-Broglie wavelength
of this electron would be
(A)0.33 nm (B)23.3 nm (C)45.6 nm (D)100 nm.
55. The wavelength associated with a golf ball weighing 200 g and moving at a speed of 5 m/h is of the
order
(A) –10
10 m (B) –20
10 m (C) –30
10 m (D) –40
10 m..
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9. ATOMICSTRUCTURE CHEMISTRY
56. An electron in a H-like atom is in an excited state. It has a total energy of –3.4 eV, calculate the
de-Broglie’s wavelength?
(A)66.5Å (B)6.66Å (C)60.6Å (D)6.06Å
Quantum Number
57. Non-directional orbital is
(A) 3s (B)4f (C) 4d (D) 4p
58. For a ‘d’ electron, the orbital angular momentum is [IIT-1997]
(A) 6 (B) 2 (C)  (D) 2
59. Which of the following represents the correct set of the four quantum numbers of 4d–electrons ?
(A) 4, 3, 2, +
1
2
(B) 4, 2, 1, 0 (C) 4, 3, -2,
1
2
(D) 4, 2, 1,
1
2

60. When the value of the azimuthal quantum number is 3, the maximum and the minimum values of the
spin multiplicities are  2S 1
(A) 4, 3 (B) 8, 1 (C) 1, 3 (D) 8, 2
LEVEL - III
61. The ratio of the radii of the first three Bohr orbits is:
(A)1 : 0.5 : 0.33 (B)1 : 2 : 3 (C)1 : 4 : 9 (D)1 : 8 : 27
62. An electron has wavelength 1Å. The potential by which the electron is accelerated will be
(A)0.0926 V (B)0.0502 V (C)0.0826 V (D)51.2 V
63. Which of the following arrangement of two electrons in two degenerated orbitals is not
possible at all
(A) (B) (C) (D)All
64. A compound of vanadium possesses a magnetic moment of 1.73 BM. the oxidation state of vanadium
in this compounds is:
(A)1 (B)2 (C)4 (D)can not be predicted
65. Uncertainty in position and momentum are equal. Uncertainty in velocity is
(A) h /  (B) h / 2 (C)1/2m h /  (D)
1
4 2
w
m 
66. The atomic spectrum of Li+2
– ion arises due to the transition of an electron from n2
to
n1
. If n1
+ n2
= 4 and (n2
– n1
) = 2, find the wavelength of 3rd
line of this series in Li+2
-ion?
(A)1.08 nm (B)10.8 nm (C)108 nm (D)1080 nm
67. An electron in a Bohr orbit of hydrogen atom with the quantum no. n2
has an angular momentum
4.2176  10–34
kg m2
s–1
. If electron drops from this level to the next lower level. Find the wavelength
of this line?
(A)18.75  10–7
m (B)1.87  10–7
m (C)187.5  10–7
m (D)0.187  10–7
m
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10. ATOMICSTRUCTURE CHEMISTRY
68. The value of the magnetic moment of a particular ion is 2.83 Bohr magneton. The ion is
(A) Fe2+
(B) Ni2+
(C) Mn2+
(D) Co3+
69. The number of spherical nodes in 3p orbitals is
(A) one (B) three (C) two (D) zero
70. Which of the following electronic configurations have zero spin multiplicity?
(A) (B)
(C) (D)
MULTIPLE CORRECT ANSWER TYPE
LEVEL - I
1. Which of the following orbitals are associated with the angular nodes?
(A) s-orbials (B) p-orbitals
(C) d-orbitals (D) f-orbitals
2. Which of the following quantum numbers is/are not allowed?
(A) n 3, 2,m 0  l (B) n 2, 2,m 1   l
(C) n 3, 0, m 1  l (D) n 5, 2, m 1   l
3. For radial probability distribution curves, which of the following is/are correct?
(A) The number of maxima in ‘2s’ orbital are two
(B) The number of spherical or radial nodes is equal to n 1 l
(C) The number of angular nodes are l
(D) 2
z3d has two angular nodes
4. Which of the following is/are correct energy order for H-atom?
(A) 1s < 2s < 2p < 3s < 3p (B) 1s < 2s = 2p < 3s = 3p
(C) 1s < 2p < 3d < 4s (D) 1s < 2s < 4s < 3d
5. The number of electrons in Na(11) having 0l are equal to
(A) There are two electrons in 1s orbital
(B) There are two electrons in 2s orbital
(C) There are two electrons in 2p orbital
(D) There are one electrons in 3s orbital
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