Class 12 Physics Chapter 12 Atoms MCQs

1 In the ground state in …A… electrons are in stable equilibrium while in …B… electrons always experiences a net force. Here, A and B refer to

A Dalton’s theory, Rutherford model

B Rutherford’s model, Bohr’s model

C Thomson’s model, Rutherford’s model

D Rutherford’s model, Thomson’s model

View Answer

Answer:Thomson’s model, Rutherford’s model

2 The angular momentum of the electron in hydrogen atom in the ground state is

A 2h

B h/2

C h/2π

D h/4π

View Answer

Answer:h/2π

3 As the quantum number increases, the difference of energy between consecutive energy levels

A remain the same

B increases

C decreases

D sometimes increases and sometimes decreases.

View Answer

Answer:decreases

4 In a Rutherford scattering experiment when a projectile of charge Z₁ and mass M1 approaches a target nucleus of charge Z₂ and mass M₂, the distance of closest approach is r₀. The energy of the projectile is

A directly proportional to Z₁ Z₂

B inversely proportional to Z₁

C directly proportional to mass M₁

D directly proportional to M₁ × M₂

View Answer

Answer:directly proportional to Z₁ Z₂

5 Rutherford’s α-particle experiment showed that the atoms have

A Proton

B Nucleus

C Neutron

D Electrons

View Answer

Answer:Nucleus

6 The Rutherford α-particle experiment shows that most of the α-particles pass through almost unscattered while some are scattered through large angles. What information does

A Atom is hollow.

B The whole mass of the atom is concentrated in a small centre called nucleus

C Nucleus is positively charged

D All of the above

View Answer

Answer:All of the above

7 According to Bohr’s model of hydrogen atom

A the linear velocity of the electron is quantised.

B the angular velocity of the electron is quantised.

C the linear momentum of the electron is quantised.

D the angular momentum of the electron is quantised.

View Answer

Answer:the angular momentum of the electron is quantised.

8 According to the Bohr theory of H-atom, the speed of the electron, its energy and the radius of its orbit varies with the principal quantum number n, respectively, as

A 1/n, n², 1/n²

B n, 1/n², n²

C n, 1/n², 1/n²

D 1/n, 1/n², 1/n²

View Answer

Answer:1/n, 1/n², 1/n²

9 The first spectral series was disscovered by

A Balmer

B Lyman

C Paschen

D Pfund

View Answer

Answer:Balmer

10 When an electron jumps from the fourth orbit to the second orbit, one gets the

A second line of Paschen series

B second line of Balmer series

C first line of Pfund series

D second line of Lyman series

View Answer

Answer:second line of Balmer series

11 The Balmer series for the H-atom can be observed

A if we measure the frequencies of light emitted when an excited atom falls to the ground state

B if we measure the frequencies of light emitted due to transitions between excited states and the first excited state

C in any transition in a H-atom

D None of these

View Answer

Answer:if we measure the frequencies of light emitted due to transitions between excited states and the first excited state

12 In Balmer series of emission spectrum of hydrogen, first four lines with different wavelength H_α H_β H_γ and H_δ are obtained. Which line has maximum frequency out of these?

A H_α

B H_β

C H_γ

D H_δ

View Answer

Answer:H_δ

13 In which of the following series, does the 121.5 nm line of the spectrum of the hydrogen atom lie ?

A Lyman series

B Balmer series

C Paschen series

D Brackett series.

View Answer

Answer:Lyman series

14 Which of the following series in the spectrum of hydrogen atom lies in the visible region of the electromagnetic spectrum?

A Paschen series

B Balmer series

C Lyman series

D Brackett series

View Answer

Answer:Balmer series

15 The shortest wavelength in Balmer’s series for Hydrogen atom is …A… and this is obtained by substituting …B … in Balmer’s formula. Here, A and B refer to

A 656.3 nm, n = 3

B 486.1 nm, n = 4

C 410.2 nm, n = 5

D 364.6 nm, n = ∞

View Answer

Answer:364.6 nm, n = ∞

16 As an electron makes a transition from an excited state to the ground state of a hydrogen – like atom/ion

A kinetic energy decreases, potential energy increases but total energy remains same

B kinetic energy and total energy decrease but potential energy increases

C its kinetic energy increases but potential energy and total energy decrease

D kinetic energy, potential energy and total energy decrease

View Answer

Answer:its kinetic energy increases but potential energy and total energy decrease

17 In a hydrogen atom, which of the following electronic transitions would involve the maximum energy change

A n = 2 to n = 1

B n = 3 to n = 1

C n = 4 to n = 2

D n = 3 to n = 2

View Answer

Answer:n = 3 to n = 1

18 Hydrogen atom excites energy level from fundamental state to n = 3. Number of spectral lines according to Bohr, is

A 4

B 3

C 1

D 2

View Answer

Answer:3

19 The transition from the state n = 4 to n = 3 in a hydrogen like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from

A 2 → 1

B 3 → 2

C 4 → 2

D 5 → 4

View Answer