1. Which of the following defines the Mass number of an atom?
a.number of protons + number of electrons
b.number of neutrons + number of electrons
c.number of protons + number of neutrons
d.number of electrons
Answer (c). number of protons + number of electrons
2. Who is credited with the discovery of electron?
a.JJ Thomson
b.James Chadwick
c.Ernest Rutherford
d.Niels Bohr
Answer (a). JJ Thomson
3. An atom has a mass number of 37 and atomic number 17. How many protons does it have?
a.20
b.17
c.54
d.21
Answer (b). 17
4. Which of the following mostly accounts for the mass of an atom?
a.neutrons
b.neutron and proton
c.electron and proton
d.electron and neutron
Answer (b).
5. Within an atom, the nucleus when compared to the extra nuclear part is
a.bigger in volume and heavier in mass
b.smaller in volume but heavier in mass
c.smaller in volume and lighter in mass
d.same size
Answer (b). smaller in volume but heavier in mass
6. What would be the atomic number of the element in whose atom the K and L shells are full?
a.10
b.12
c.14
d.16
Answer (a). 10
7. Which metal was used by Rutherford in his alpha-scattering experiment?
a.gold
b.platinum
c.silver
d.lead
Answer (a). gold
8. An element has an electronic configuration of 2, 8, 7. Its valency is
a.2
b.7
c.3
d.1
Answer (d). 1
9. During a chemical reaction, atomic number
a.changes
b.remains same
c.changes and then is restored
d.changes alternately
Answer (b). remains same
10. Which isotope of hydrogen contains only one proton and no neutron in its nucleus?
a.protium
b.deuterium
c.tritium
d.None of the above
Answer (a). protium
11. Who of the following was awarded the Nobel Prize for his measurement of elementary electronic charge?
a.Rutherford
b.Robert Millikan
c.James Chadwick
d.JJ Thomson
Answer (b). Robert Millikan
12. How are the subshells in an atom labelled?
a.s, p, d, f, g
b.s, p, f, g, d
c.s, f, g, d, f
d.s, d, g, p, f
Answer (a). s, p, d, f, g
13. The isotopes of neutral atoms of an element differ in
a.Atomic number
b.Mass number
c.Number of electrons
d.Chemical properties
Answer (b). Mass number
14. The electronic configuration of an atom having atomic number 20 is
a.2, 8, 8, 2
b.2, 8, 10
c.2, 6, 8, 4
d.2, 4, 8, 6
Answer (a). 2, 8, 8, 2
15. Almost the entire mass of an atom is concentrated in the
a.proton
b.electrons
c.nucleus
d.neutrons
Answer (c). nucleus
16. An atom differs from its ion in
a.Nuclear charge
b.Mass number
c.Number of electrons
d.Number of neutrons
Answer (c). Number of electrons
17. The proton is heavier than an electron by
a.187 times
b.1837 times
c.3837 times
d.2827 times
Answer (b). 1837 times
18. Which of the following is true about a charged atom?
a.anion is negatively charged
b.cation is negatively charged
c.cation has gained an electrond.
anion has lost an electron
Answer (a).a.anion is negatively charged
19. Which of the following is not a fundamental particle?
a.Proton
b.Neut0ron
c.Alpha particle
d.Electron
Answer (c). Alpha particle
20. Which one among the following most correctly determines the atomic number of an element?
a. Number of protons
b. Number of protons and electrons
c. Number of ions
d. Number of nucleons
Answer (a). Number of protons
21. How many electrons does the outermost shell of neon have?
a. 4
b. 8
c. 2
d. 16
Answer (b). 8
23. Which of the following determines the chemical properties of an element?
a. Number of electrons
b. Number of neutrons
c. Number of protons
d. All of the above
Answer (a). Number of electrons
24. The number of protons in a negatively charged atom (anion) is
a. more than the atomic number of the element
b. less than the atomic number of the element
c. more than the number of electrons in the atom
d. less than the number of electrons in the atom
Answer (d). less than the number of electrons in the atom
25. Atoms which have same mass number but different atomic number are called
a. isotopes
b. isomers
c. isotones
d. isobars
Answer (d). isobars
26. The atomic theory of matter was first proposed by
a. John Dalton
b. Rutherford
c. J. J. Thomson
d. Niels Bohr
Answer (a). John Dalton
27. How many orbitals can have the following set of quantum numbers, n = 3, l = 1, m1 = 0 ?
a) 3
b) 1
c) 4
d) 2
Answer: (b). 1
28. Electronic configuration of the outer shell of the element Gd with atomic number 64 is
a) 4f4 5d5 6s1
b) 4f3 5d5 6s2
c) 4f5 5d4 6s1
d) 4f7 5d1 6s2
Answer: (d). 4f7 5d1 6s2
29. Maximum number of electrons in a subshell can be
a) 4l + 2
b) 4l – 2
c) 2n2
d) 2l + 1
Answer: (a). 4l + 2
30. The orientation of atomic orbitals depends on their
a) spin quantum number
b) magnetic quantum number
c) azimuthal quantum number
d) principal quantum number
Answer: (b). magnetic quantum number
31. A gas X has Cp and Cv ratio as 1.4, at NTP 11.2 L of gas X will contain_______ number of atoms
a) 1.2 × 1023
b) 3.01 × 1023
c) 2.01 × 1023
d) 6.02 × 1023
Answer: (d)
32. Number of unpaired electrons in N2+
a) 3
b) 1
c) 2
d) 0
Answer: (b). 1
33. The excitation energy of a hydrogen atom from its ground state to its third excited state is
a) 12.75 eV
b) 0.85 eV
c) 10.2 eV
d) 12.1 eV
Answer: (a). 12.75 eV
34. 3p orbital has _____ radial nodes
a) three
b) two
c) one
d) none
Answer: (c). one
35. A 0.66 kg ball is moving with a speed of 100 m/s. Find its wavelength
a) 6.6 × 10-34 m
b) 6.6 × 10-32 m
c) 1.0 × 10-32 m
d) 1.0 × 10-35 m
Answer: (d). 1.0 × 10-35 m
36. Which among the following has the shortest C-C bond length?
a) Ethene
b) Ethane
c) Benzene
d) Ethyne
Answer: (d). Ethyne
37. The oxygen molecule is paramagnetic. It can be explained by
a) Resonance
b) Hybridisation
c) Valence bond theory
d) Molecular orbital theory
Answer: (d). Molecular orbital theory
38. Find the paramagnetic species
a) CN–
b) NO+
c) CO
d) O2–
Answer: (d). O2–
39. Find the diamagnetic species
a) H2
b) H2–
c) He2+
d) H2+
Answer: (a). H2
40. Which of the following pairs has the same bond order?
a) O2+, NO+
b) N2, O2
c) O22-, B2
d) NO, CO
Answer: (c). O22-, B2
41. Each P of P4O10 is attached to how many oxygen atoms?
a) 3
b) 2.5
c) 2
d) 4
Answer: (d). 4
42. When O2 changes to O2–, the electron goes to which of the orbitals?
a) 𝜋 orbital
b) 𝜎 orbital
c) 𝜋* orbital
d) 𝜎* orbital
Answer: (c). 𝜋* orbital
43. O-O bond length is minimum in
a) O2–
b) O2
c) O2+
d) O22-
Answer: (c). O2+
44. Which of the following is not paramagnetic?
a) CO
b) N2+
c) NO
d) O2–
Answer: (a). CO
45. Find the molecule having the highest bond order
a) O2+
b) O2–
c) O22-
d) O2
Answer: (a). O2+
46. C-O bond length is minimum in
a) CO2
b) CO32-
c) HCOO–
d) CO
Answer: (d). CO
47. Molecules are held together in a crystal by
a) hydrogen bond
b) electrostatic attraction
c) Van der Waal’s attraction
d) dipole-dipole attraction
Answer: (c). Van der Waal’s attraction
48. Sp3d2 hybridization is present in [Co(NH3)63+], find its geometry
a) octahedral geometry
b) square planar geometry
c) tetragonal geometry
d) tetrahedral geometry
Answer: (a). octahedral geometry
49. Find the molecule with the maximum dipole moment
a) CH4
b) NH3
c) CO2
d) NF3
Answer: (b). NH3
50. MX6 is a molecule with octahedral geometry. How many X – M – X bonds are at 180°?
a) four
b) two
c) three
d) six
Answer: (c). three
51. Find the pair with sp2 hybridisation of the central molecule
a) NH3 and NO2–
b) BF3 and NH2–
c) BF3 and NO2–
d) NH2– and H2O
Answer: (c). BF3 and NO2–
52. The formal charge and P-O bond order in PO43- respectively are
a) 0.6, -0.75
b) -0.75, 1.25
c) 1.0, -0.75
d) 1.25, -3
Answer: (b). -0.75, 1.25
53. Which of the molecules does not have a permanent dipole moment?
a) SO3
b) SO2
c) H2S
d) CS2
Answer: (d). CS2
54. pℼ – dℼ bonding is present in which molecule
a) SO32-
b) CO32-
c) NO3–
d) BO33-
Answer: (a). SO32-
55. Which one has a pyramidal shape?
a) SO3
b) PCl3
c) CO32-
d) NO3–
Answer: (b). PCl3
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