1. The spectrum of He is expected to be similar to that
(a) H
(b) Li+
(c) Na
(d) He+
2. The number of spherical nodes in 3p orbitals are
(a) one
(b) three
(c) none
(d) two
3. If r is the radius of the first orbit, the radius of nth orbit of H-atom is given by
(a) rn2
(b) rn
(c) r/n
(d) r2n2
4. Which of the following statements do not form a part of Bohr’s model of hydrogen atom?
(a) Energy of the electrons in the orbits are quantized
(b) The electron in the orbit nearest the nucleus has the lowest energy
(c) Electrons revolve in different orbits around the nucleus
(d) The position and velocity of the electrons in the orbit cannot be determined simultaneously.
5. Number of unpaired electrons in N2+is
(a) 2
(b) 0
(c) 1
(d) 3
6. The maximum number of electrons in a subshell is given by the expression
(a) 4l – 2
(b) 4l + 2
(c) 2l + 2
(d) 2n2
7. The total number of electrons that can be accommodated in all the orbitals having principal quantum number 2 and azimuthal quantum number 1 is
(a) 2
(b) 4
(c) 6
(d) 8
8. An ion has 18 electrons in the outermost shell, it is
(a) Cu+
(b) Th4+
(c) Cs+
(d) K+
9. In a given atom no two electrons can have the same values for all the four quantum numbers. This is called
(a) Hund’s Rule
(b) Aufbau principle
(c) Uncertainty principle
(d) Pauli’s Exclusion principle.
10. For azimuthal quantum number l = 3 , the maximum number of electrons will be
(a) 2
(b) 6
(c) 0
(d) 14
11. The order of filling of electrons in the orbitals of an atom will be
(a) 3d, 4s, 4p, 4d, 5s
(b) 4s, 3d, 4p, 5s, 4d
(c) 5s, 4p, 3d, 4d, 5s
(d) 3d, 4p, 4s, 4d, 5s
13. Which of the following species has four lone pairs of electrons in outer shell ?
(a) I
(b) O–
(c) Cl–
(d) He
- If ionization potential for hydrogen atom is 13.6 eV, then ionization potential for He+will be
(a) 54.4 eV
(b) 6.8 eV
(c) 13.6 eV
(d) 24.5 eV - The uncertainty in the position of an electron is equal to its de Broglie wavelength. The minimum percentage error in its measurement of velocity under this circumstance will be approximate:
(a) 4
(b) 8
(c) 2
(d) 18
16. Which of the following is never true for cathode rays?
(a) They possess kinetic energy
(b) They are electromagnetic waves
(c) They produce heat
(d) They produce mechanical pressure.
17. The electron was shown experimentally to have wave properties by
(a) de Broglie
(b) Davisson and Germer
(c) N. Bohr
(d) Schrodinger.
18. When an electron of charge e and mass m moves with a velocity v about the nuclear charge Ze is circular orbit of radius r, the potential energy of the electrons is given by
(a) Ze2/r
(b) –Ze2/r
(c) Ze2/2r
(d) mv2/r
19. In the photo-electron emission, the energy of the emitted electron is
(a) greater than the incident photon
(b) same as than of the incident photon
(c) smaller than the incident photon
(d) proportional to the intensity of incident photon.
20. If electron has spin quantum number + 2/1 and a magnetic quantum number -1, it cannot be present in
(a) d-orbital
(b) f-orbital
(c) p-orbital
(d) s-orbital
(b) O2+
(c) O2–
(d) N2+
(c) 656 nm
(d) 0.656 nm
30. Set of isoelectronic species is
(a) N2,CO2,CN-,O
(b) N,H2S,CO
(c) N2 , CO, CN- , O2+2
(d) Ca,Mg,Cl
31. The following quantum numbers are possible for how many orbital n = 3, l = 2, m =+2?
(a) 1
(b) 3
(c) 2
(d) 4
32. Which of the following is isoelectronic?
(a) CO2, NO2
(b) NO2–, CO2
(c) CN–, CO
(d) SO2, CO2
33. In hydrogen atom, energy of first excited state is –3.4 eV. Find out KEof the same orbit of Hydrogen atom
(a) + 3.4 eV
(b) + 6.8 eV
(c) – 13.6 eV
(d) + 13.6 eV
34. The value of Planck’s constant is 6.63 × 10-34 Js. The velocity of light is 3.0 × 108m sWhich value is closest to the wavelength in nanometers
of a quantum of light with frequency of 8 × 1015 s-1?
(a) 3 × 107(b) 2 × 10-25
(c) 5 × 10-18
(d) 4 × 101
35. The ions O2- , F– , Na+, Mg2+ and Al3+ are isoelectronic. Their ionic radii show (a) Adecrease from O2-to F–and then increase from Na+ to Al3+
(b) Asignificant increase from O2- to Al3+
(c) Asignificant decrease from O2- to Al3+
(d) An increase from O2- to F– and then decrease from Na+to Al3+
36. The frequency of radiation emitted when the electron falls from n = 4 to n = 1 in a hydrogen atom will be (Given ionization energy of H=2.18 ×10-18J atom-1and h = 6.625 × 10-34 Js)
(a) 1.54´ 1015 s-1
(b) 1.03 ´ 1015 s-1
(c) 3.08 ´ 1015 s-1
(d) 2.00´ 1015 s-1
37. The energy of second Bohr orbit of the hydrogen atom is 328 kJmol1; hence the energy of fourth Bohr orbit would be:
(a) 41- kJmol-1
(b) 82- kJmol-1
(c) 164- kJmol-1
(d) 1312- kJmol-1
38. Given: The mass of electron is 9.11 × 10-31 kg Plank constant is 6.626 × 10–34 Js, the uncertainty involved in the measurement of velocity within a distance of 0.1 A is
(a) 5.79 × 107ms-1
(b) 5.79 × 108ms-1
(c) 5.79 × 105ms-1
(d) 5.79 × 106ms-1
39. The orientation of an atomic orbital is governed by
(a) Spin quantum number
(b) Magnetic quantum number
(c) Principal quantum number
(d) Azimuthal quantum number
40. Consider the following sets of quantum numbers :
n l m s
(i) 3 0 0 +1/2
(ii) 2 2 1 +1/2
(III) 4 3 -2 -1/2
(iv) 1 0 -1 -1/2
(v) 3 2 3 +1/2
Which of the following set of quantum number is not possible ?
(a) , (ii) , (iii) and (iv)
(b) (ii) , (iv) and
(c) and (iii)
(d) (ii) , (iii) and (iv)
which is equal to 1 × 10-18g cm s-1. The uncertainty in electron velocity is, (mass of an electron is 9 × 10-28g)
(a) 1 × 109cm s-1
(b) 1 × 106cm s-1
(c) 1 × 105cm s-1
(d) 1 × 1011cm s-1
43. The energy absorbed by each molecule (A2) of a substance is 4.4 × 1019Jand bond energy per molecule is 4.0 × 1019J. The kinetic energy of the molecule per atom will be:
(a) 2.2 × 10-19J
(b) 2.0 × 10-19J
(c) 4.0 × 10-20J
(d) 2.0 × 10-20J
44. Maximum number of electrons in a subshell of an atom is determined by the following:
(a) 2 l + 1
(b) 4 l – 2
(c) 2 n2
(d) 4 l + 2
45. Which of the following is not permissible arrangement of electrons in an atom?
(a) n = 5, l = 3, m = 0, s = + 2/1
(b) n = 3, l = 2, m = – 3, s = – 2/1
(c) n = 3, l = 2, m = – 2, s = – 2/1
(d) n = 4, l = 0, m = 0, s = – 2/1
56. The correct set of four quantum numbers for the valence electron of rubidium atom (Z= )37 is
(a) 5, 1, + 2/1
(b) 6, 0, 2/1 + 0
(c) 5, 0, 2/1 + 0
(d) 5, 1, 2/1 + 0
64. Which of the following series of transitions in the spectrum of hydrogen atom falls in visible region?
(1) Lyman series
(2) Balmer series
(3) Paschen series
(4) Brackett series
SOLTIONS
1.(B) Both He and Li+ contains 2 electrons each therefore their spectrum will be similar.
2.(a) No of radial nodes in 3p orbital
= (n – l – 1)
[for p orbital l =1 ]
= 3 – 1 – 1
= 1
3.(a) Radius of nth orbit = r1n2(for H-atom)
4. (D) is uncertainty principle which was given by Hisenberg and not Bohr’s postulate
5. (c) N(7) = 1s2 2s2 2p2 N2+(s) = 1s2‑ , 2s22 Unpaired electrons =1.
6.(B) No of orbitals in a sub shell = 2l +1No of electons = 2(2l+1) =4l+2
7. (c) n = 2 , l =1 means 2p – orbital. Electrons that can be accommodated = 6 as p sub –shell has 3 orbital and each orbital contains 2 electrons
8.(A)The electronic configuration of Cu,Th,Cs and K are Cu(29)=2,8,18,1 Cu+=2,8,18 Th(90)=2,8,18,32,18,10,2 Th4+=2,8,18,32,18,8 s(55)=2,8,18,18,8,1Cs+=2,8,18,18,8 K(19)=2,8,8,1K+=2,8,8 Thus, Cu+has 18 electrons in the outermost shell.
9. (d) This is as per the definition of Pauli’s Exclusion princieple
10. (D) l = 3 means f –subshell. Maximum no of electrons = 4l +2 = 4 ´3+2 = 14
11. (B)using n+l rule 3d⇒3+2=5 4s⇒4+0=4 4p⇒4+1=5 4d⇒4+2=6 5s⇒5+0=5 4s,3d,4p,5s,4d 4s,3d,5s,4d
12. (c) Energy of an electron in Bohr’s orbit is given by the relationship. En = – eV.
13. (c) Consider the electronic configuration of each of these options:-
A) I – [Kr]4d105s25p5→ 3 lone pairs.
B) O− – 1s22s22p5→ 3 lone pairs.
C) Cl− – 1s22s22p63s23p6→ 4 lone pairs.
D) He – 1s2→ 1 lone pair. Hence option C is the right answer.
14. Energy of electron in nth orbit of a hydrogen-like species = eV Ionization potential =13.6Z2 For H,Z =1 He+,Z =2.
∴ Ionization potential of He+ =13.6×22 =54.4 eV
15(b) The uncertainty in position is equal to de Broglie wavelength. ⟹Δx = λ = ……. (1) The Heisenberg’s uncertainty principle is ΔxΔv≥ …… (2) From equations (1) and (2), ( Δv ≥ ) Thus, ≥ Hence, minimum percentage error = ´ 100 ≥ = =7.96≈8.
16. (b) cathode rays are never electromagnetic waves.
17.(b) Wave nature of electron was shown by Davisson and Germer. Davission and germer demonstrated the physical reality of the wave nature of electrons by showing that a beam of electrons could also diffracted by crystals just like light of x-rays.
19. (c) K.E of emitted electron = hv – hv0 ( i.e. smaller than hv)
23. (d) The orbitals which have same energy are called degenerate orbitals e.g. Px,Py, Pz
24.(C) Acc to deBroglie
25. (a) We know that ions which have the same number of electrons are called isoelectronic. We also know that both CO and CN– have 14 electrons, therefore these are isoelectronic.
26. (d)Given :Radius of hydrogen atom =0.530 ,Number of excited state (n) = 2 and Atomic number of hydrogen atom (z) = We know that the Bohr radius.
27. (d)By Heisenberg’s Uncertainity principle,
Position of both an electron & a helium atom =1 nm Momentum of an electron =5×10−25 kg.m/s When the position of both the electron and helium atom is same then the momentum of helium atom is equal to momentum of an electron. Momentum of Helium atom =5×10−26 Kg.m/s.
28. (c) Energy of electron in 2nd orbit of Li2+
Energy required = 0 – (-30.6) = 30.6 eV
29. (c) Energy of photon, E=hc/λ or λ=hc/E Where, h=6.626×10−34Js,c=3×108ms−1 Given E=3.03×10−19J/atom By putting all these values, we get-
λ=6.626×10−34×3×108/(3.03×10−19) λ=6.56×10−7m =656nm
30. (c) The molecule which contains same number of electron are called isoelectronic e.g.
31. (a) Quantum number n = 3 , l =2 , m = +2 represent an orbital with
32.(c) Both CN– and CO have 14 electons
33. (a) The energy in an excited state is nothing but kinetic energy.
35.(c) Among isoelectronic species, ionic radii of anion is more than that of cations. Further size of anion increase with increase in –ve change and size of cation decrease with increase in +ve charge. Hence ionic radii decreases from O– to Al+++
Given that-
h=6.626×10−34J−s
m=9.11×10−31kg
40. (b) (ii) is not possible for any value of n because l varies from 0 to (n-1) thus for n=2 ,l can be only 0,1,2.
(iv) is not possible because for l= 0 , m = 0
(v) is not possible because for l=2, m varies from -2 to +2
41. (a)According to Heisenberg’s uncertainity principle,
42. The measurement of the electron position if associated with an uncertainty in momentum, which is equal to 1 × 10-18g cm s-1. The
uncertainty in electron velocity is, (mass of an electron is 9 × 10-28g)
(a) 1 × 109cm s-1
(b) 1 × 106cm s-1
(c) 1 × 105cm s-1
(d) 1 × 1011cm s-1
43. The energy absorbed by each molecule (A2) of a substance is 4.4 × 1019Jand bond energy per molecule is 4.0 × 1019J. The kinetic energy of the molecule per atom will be:
(a) 2.2 × 10-19J
(b) 2.0 × 10-19J
(c) 4.0 × 10-20J
(d) 2.0 × 10-20J
44. Maximum number of electrons in a subshell of an atom is determined by the following:
(a) 2 l + 1
(b) 4 l – 2
(c) 2 n2
(d) 4 l + 2
45. Which of the following is not permissible arrangement of electrons in an atom?
(a) n = 5, l = 3, m = 0, s = + 2/1
(b) n = 3, l = 2, m = – 3, s = – 2/1
(c) n = 3, l = 2, m = – 2, s = – 2/1
(d) n = 4, l = 0, m = 0, s = – 2/1
46. According to MO theory which of the following lists ranks the nitrogen species in terms of increasing bond order?
47. Which one of the following species does not exist under normal conditions?
(a) Be2+
(b) Be2
(c) B2
(d) Li2
48. A 066. kg ball is moving with a speed of 100 m/s. The associated wavelength will be ( h=6.6 × 10-34Js)
(a) 1.0 u 10–32m
(b) 6.6 u 10–32m
(c) 6.6 u 10–34m
(d) 1.0 u 10–35m
49. The total number of atomic orbitals in fourth energy level of an atom is:
(a) 8
(b) 16
(c) 32
(d) 4
50. Which of the following has the minimum bond length?
(a) O2+
(b) O2 –
(c) O22-
(d) O2
56. The correct set of four quantum numbers
for the valence electron of rubidium atom (Z=
)37 is
(a) 5, 1, + 2/1
(b) 6, 0, 2/1 + 0
(c) 5, 0, 2/1 + 0
(d) 5, 1, 2/1 + 0
in energy when the electron changes orbit. (c) For n = 1, the electron has a more negative energy than it does for n = 6 which mean that the electron is more loosely bound in the smallest allowed orbit. (d) The negative sign in equation simply means that the energy or electron bound to the nucleus is lower than it would be if the electrons were at the infinite distance from the nucleus.
SOLTIONS
1.(B) Both He and Li+ contains 2 electrons each therefore their spectrum will be similar.
2.(a) No of radial nodes in 3p orbital
= (n – l – 1)
[for p orbital l =1 ]
= 3 – 1 – 1 = 1
3.(a) Radius of nth orbit = r1n2(for H-atom)
14.Energy of electron in nth orbit of a hydrogen-like species
18.(b)
39. (b) Magnetic quantum no. represents the orientation of atomic orbitals in an atom. For example Px, Py & PZ have orientation along X-axis , Y-axis& Z-axis
40. (b)(ii) is not possible for any value of n because l varies from 0 to (n-1) thus for n=2 ,l can be only 0,1,2.
(iv) is not possible because for l= 0 , m = 0
(v) is not possible because for l=2, m varies from -2 to +2
41. (a)According to Heisenberg’s uncertainity principle,
47. (b) Bond order of Be2 = 0 , hence Be2 cannot exist
Given n =4 hence number of atomic orbitals in 4th shell will be 16.
60. (c) Energy of an electron at infinite distance from the nucleus is zero. As an electron approaches the nucleus, the electronattraction increases and hence the energy of electron decreases and thus becomes negative. Thus as the value of n decreases, i.e. lower the orbit is, more negative is the energy of the electron in it.
