# Planck’s Quantum Theory Questions and Answers Rutherford’s experiment, Bohr’s model, Davisson and Germer’s experiment, electromagnetic radiation, Heisenberg’s uncertainty principle, Ohm’s law, Atomic models and Planck’s quantum theory practice questions.

Ques. The formation of energy bonds in solids are in accordance with
(a) Heisenberg’s uncertainty principle
(b) Bohr’s theory
(c) Ohm’s law
(d) Rutherford’s atomic model

Ans. (b)

Ques. Wavelength of spectral line emitted is inversely proportional to
(b) Energy
(c) Velocity
(d) Quantum number

Ans. (b)

Ques. The ratio of area covered by second orbital to the first orbital is
(a) 1 : 2
(b) 1 : 16
(c) 8 : 1
(d) 16 : 1

Ans. (d)

Ques. Bohr model of atom is contradicted by
(a) Pauli’s exclusion principle
(b) Planck quantum theory
(c) Heisenberg uncertainty principle
(d) All of these

Ans. (c)

Ques. The value of the energy for the first excited state of hydrogen atom will be
(a) –13.6 eV
(b) –3.40 eV
(c) –1.51 eV
(d) –0.85 eV

Ans. (b)

Ques. The ratio between kinetic energy and the total energy of the electrons of hydrogen atom according to Bohr’s model is
(a) 2 : 1
(b) 1 : 1
(c) 1 : – 1
(d) 1 : 2

Ans. (c)

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Ques. The ionisation potential of a hydrogen atom is –13.6 eV. What will be the energy of the atom corresponding to n = 2
(a) – 3.4 eV
(b) – 6.8 eV
(c) – 1.7 eV
(d) – 2.7 eV

Ans. (a)

Ques. The energy of electron in hydrogen atom in its grounds state is –13.6 eV. The energy of the level corresponding to the quantum number equal to 5 is
(a) –0.54 eV
(b) – 0.85 eV
(c) – 0.64 eV
(d) – 0.40 eV

Ans. (a)

Ques. The positive charge of an atom is
(a) Spread all over the atom
(b) Distributed around the nucleus
(c) Concentrated at the nucleus
(d) All of these

Ans. (c)

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Ques. The radius of the nucleus is related to the mass number A by
(a) R = RoA1/2
(b) R = RoA
(c) R = RoA2
(d) R = RoA1/3

Ans. (d)

Ques. If electron falls from n = 3 to n = 2,, then emitted energy is
(a) 10.2eV
(b) 12.09 eV
(c) 1.9 eV
(d) 0.65 eV

Ans. (c)

Ques. The element used by Rutherford in his famous scattering experiment was
(a) Gold
(b) Tin
(c) Silver

Ans. (a)

Ques. In an element going away from nucleus, the energy of particle
(a) Decreases
(b) Not changing
(c) Increases
(d) None of these

Ans. (c)

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Ques. An electronic transition from 1s orbital of an atom causes
(a) Absorption of energy
(b) Release of energy
(c) Both release or absorption of energy
(d) Unpredictable

Ans. (a)

Ques. The first use of quantum theory to explain the structure of atom was made by
(a) Heisenberg
(b) Bohr
(c) Planck
(d) Einstein

Ans. (b)

Ques. In Balmer series of hydrogen atom spectrum which electronic transition causes third line
(a) Fifth Bohr orbit to second one
(b) Fifth Bohr orbit to first one
(c) Fourth Bohr orbit to second one
(d) Fourth Bohr orbit to first one

Ans. (a)

Ques. Who modified Bohr’s theory by introducing elliptical orbits for electron path?
(a) Hund
(b) Thomson
(c) Rutherford
(d) Sommerfield

Ans. (d)

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Ques. When an electron revolves in a stationary orbit then
(a) It absorbs energy
(b) It gains kinetic energy
(d) Its energy remains constant

Ans. (d)

Ques. The energy of second Bohr orbit of the hydrogen atom is –328 kJ mol–1, hence the energy of fourth Bohr orbit would be
(a) – 41 kJ mol–1
(b) –1312 kJ mol–1
(c) –164 kJ mol–1
(d) – 82 kJ mol–1

Ans. (d)

Ques. The postulate of Bohr theory that electrons jump from one orbit to the other, rather than flow is according to
(a) The quantisation concept
(b) The wave nature of electron
(c) The probability expression for electron
(d) Heisenberg uncertainty principle

Ans. (a)

Ques. Which of the following statements does not form part of Bohr’s model of the hydrogen atom
(a) Energy of the electrons in the orbit is 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

Ans. (d)

Ques. Experimental evidence for the existence of the atomic nucleus comes from
(a) Millikan’s oil drop experiment
(b) Atomic emission spectroscopy
(c) The magnetic bending of cathode rays
(d) Alpha scattering by a thin metal foil

Ans. (d)

Ques. When an electron drops from a higher energy level to a low energy level, then
(a) Energy is emitted
(b) Energy is absorbed
(c) Atomic number increases
(d) Atomic number decreases

Ans. (a)

Ques. 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 the electron undergoing the transition

Ans. (c)

Ques. Electron occupies the available orbital singly before pairing in any one orbital occurs, it is
(a) Pauli’s exclusion principle
(b) Hund’s Rule
(c) Heisenberg’s principle
(b) Prout’s hypothesis

Ans. (b)

Ques. When atoms are bombarded with alpha particles, only a few in million suffer deflection, others pass out undeflected. This is because
(a) The force of repulsion on the moving alpha particle is small
(b) The force of attraction on the alpha particle to the oppositely charged electrons is very small
(c) There is only one nucleus and large number of electrons
(d) The nucleus occupies much smaller volume compared to the volume of the atom

Ans. (d)

Ques. Rutherford’s alpha particle scattering experiment eventually led to the conclusion that
(a) Mass and energy are related
(b) Electrons occupy space around the nucleus
(c) Neutrons are buried deep in the nucleus
(d) The point of impact with matter can be precisely determined

Ans. (b)

Ques. Bohr model of an atom could not account for
(a) Emission spectrum
(b) Absorption spectrum
(c) Line spectrum of hydrogen
(d) Fine spectrum

Ans. (d)

Ques. Energy of orbit
(a) Increases as we move away from nucleus
(b) Decreases as we move away from nucleus
(c) Remains same as we move away from nucleus
(d) None of these

Ans. (a)