Atoms Mock Test – Class 12 Physics

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Quiz: Atoms – Certificate Challenge
Total questions: 437
Questions to attempt: 100 random
Time allotted: 100 minutes
Certificate pass score: 70%
Random questions: Yes
Certificate: Yes
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Progressive Test — Guest First Round

Atoms – Progressive Test

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1 / 50

1. A graph description is given below.

Horizontal energy levels are drawn for a Bohr atom. An arrow points downward from a higher level to a lower level.

The arrow represents

a) continuous radiation from an unchanged orbit

b) absorption of a photon with zero energy

c) photon emission equal to the level gap

d) disappearance of the nucleus

2 / 50

2. The hydrogen line has wavelength approximately . For the corresponding transition in , the wavelength is approximately

3 / 50

3. A spectral line splits when an external electric field is applied to the source. The limitation of Bohr’s model highlighted by this observation is its inability to fully explain

a) alpha-particle collimation

b) gold foil malleability

c) Stark effect

d) continuous gravitational orbits

4 / 50

4. In , an electron in absorbs a photon of energy . The final state of the electron is

c) ionised with zero kinetic energy

d) ionised,

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5. Study the table of hydrogen transitions.

Row	Transition	Series
P		Lyman
Q		Balmer
R		Balmer
S		Lyman

The row that needs correction is

a) Row Q

b) Row P

c) Row S

d) Row R

6 / 50

6. If the radius of an atom is and the radius of its nucleus is , the approximate ratio of atomic volume to nuclear volume is

7 / 50

7. A hydrogen atom in the ground state receives of energy. The electron can be

a) excited only to

b) excited only to

c) just ionised with zero kinetic energy

d) forced into an orbit with negative radius

8 / 50

8. Study the following energy-level table for hydrogen.

Level	Energy

The ionisation energy from is

9 / 50

9. If the same -particle passes at the same distance from two nuclei with charges and , the repulsive force near the second nucleus is

a) twice as large

b) the same

c) half as large

d) four times as large

10 / 50

10. The empirical Rydberg formula for hydrogen is used mainly to calculate

a) the speed of alpha particles in air

b) hydrogen spectral-line wavelengths

c) the thickness of the scattering foil

d) the mass number of gold nuclei

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11. In the Bohr force-balance equation, increasing while keeping fixed would require a larger electron speed because

a) the centripetal force becomes independent of

b) the inward electrostatic force becomes larger

c) the Coulomb force changes from attraction to repulsion

d) the electron charge becomes zero

12 / 50

12. Study the table below for a hydrogen atom.

Transition	Photon energy	Series
P		Lyman
Q		Balmer
R		Paschen
S		Lyman

The row that needs correction is

a) Row S

b) Row Q

c) Row P

d) Row R

13 / 50

13. In the Bohr model, the relation connects the Rydberg constant with

a) hydrogen ground-state ionisation energy

b) the radius of the gold nucleus

c) the charge of an alpha particle

d) the speed of light becoming zero in atoms

14 / 50

14. A table of model conclusions is shown below.

Row	Conclusion from Rutherford scattering	Supported?
P	Most of the atom is empty space	Yes
Q	Positive charge is concentrated in a small nucleus	Yes
R	Nearly all atomic mass is concentrated in the nucleus	Yes
S	Positive charge is uniformly spread throughout the atom	Yes

The unsupported row is

a) R

b) Q

c) P

d) S

15 / 50

15. A hydrogen atom emits a photon of energy in a transition. Using , the wavelength of the photon is closest to

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16. A hydrogen line is known to be in the visible Balmer series and is produced by the smallest possible upper level for that series. The transition is

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17. For the Balmer series limit, and . The limiting wavenumber is

18 / 50

18. The expression gives energy in joule when , , and are used in SI units. The SI unit of may be written as

19 / 50

19. As increases for hydrogen, the total energy

a) becomes more negative without limit

b) becomes positive for every

c) approaches zero from below

d) remains fixed at

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20. The ion is hydrogen-like with . Its radius in the orbit is

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21. A graph is described below.

The horizontal axis shows for hydrogen. The vertical axis shows total energy in .

The graph should be a straight line with

a) negative slope

b) positive slope

c) zero slope at all points

d) no relation to

22 / 50

22. Rutherford’s conclusion that almost all the mass of an atom is concentrated in the nucleus was supported by the fact that

a) a massive projectile needs a massive deflecting centre

b) the collimator made alpha particles heavier

c) the zinc sulphide screen had large mass

d) a light electron could easily reverse an -particle

23 / 50

23. In a scattering setup, alpha particles are fired at a thin metal foil. The feature that makes them suitable for probing positive charge inside atoms is their

a) zero mass

b) positive charge

c) negative electric charge

d) absence of kinetic energy

24 / 50

24. Rutherford’s alpha-particle scattering experiment used a beam of alpha particles because alpha particles are

a) photons of very short wavelength only

b) neutral and massless radiations

c) positively charged, massive projectiles

d) negatively charged particles lighter than electrons

25 / 50

25. The same element produces a characteristic set of spectral lines because

a) its atoms emit a random continuous range of photon energies

b) its nuclei disappear when heated

c) its atoms have a definite set of allowed energy differences

d) its electrons carry no charge in a gas

26 / 50

26. A graph is described below.

The horizontal axis shows impact parameter . The vertical axis shows scattering angle for alpha particles of the same initial kinetic energy approaching the same nucleus.

The qualitative trend of the graph should show that

a) decreases as increases

b) increases linearly with for all values

c) becomes zero only for

d) remains constant for all

27 / 50

27. A zinc sulphide screen was placed around the foil in Rutherford’s experiment. Its function was to

a) neutralise the gold foil

b) reduce the charge of the nucleus

c) produce alpha particles from light

d) detect scintillations

28 / 50

28. A model that explains alpha scattering but not atomic stability or spectra is most likely

a) de Broglie’s matter-wave interpretation alone

b) Thomson’s plum-pudding model

c) Bohr’s quantised model

d) Rutherford’s nuclear model

29 / 50

29. The Lyman series lies in the ultraviolet region mainly because its transitions end at , giving

a) the smallest possible frequencies of hydrogen

b) zero energy differences and infinite wavelengths

c) only visible red photons

d) large energy gaps and short wavelengths

30 / 50

30. An electron in a one-electron ion has orbit radius and total energy . The values of and are

31 / 50

31. A hydrogen atom in can emit photons by transitions among lower levels. The number of distinct spectral lines possible as it finally reaches is

32 / 50

32. A graph of hydrogen energy levels shows the levels getting closer together as increases. The correct reason is that

a) varies as

c) varies as

d) varies as

33 / 50

33. If an atom is mostly empty space, then the volume occupied by the nucleus must be extremely small compared with the atomic volume. This idea is consistent with

a) frequent large-angle scattering of nearly all -particles

b) no deflection of any -particle under any condition

c) rare large-angle scattering and common undeflected passage

d) complete absorption of the incident alpha beam

34 / 50

34. Assertion: The Coulomb force in Bohr’s model acts as the centripetal force for the electron.
Reason: The attractive electrostatic force between the positive nucleus and the negative electron is directed toward the nucleus.

a) Assertion is true, but Reason is false

b) Both Assertion and Reason are true, but Reason does not explain Assertion

c) Assertion is false, but Reason is true

d) Both Assertion and Reason are true, and Reason explains Assertion

35 / 50

35. A hydrogen-like ion has its orbit radius equal to . The value of for the ion is

36 / 50

36. The planetary analogy in Rutherford’s model refers to

a) electrons orbit a central positive nucleus

b) nuclei moving around electrons like planets around moons

c) electrons being electrically neutral like planets

d) atoms producing seasons as planets do

37 / 50

37. A comparison uses and . If both radii are written in femtometres, where , then the approximate atomic radius is

38 / 50

38. A data sheet lists the following conversion: . The energy in joules is

39 / 50

39. In Rutherford’s nuclear model, the force that keeps an electron moving around the nucleus is mainly

a) frictional force due to the empty space inside the atom

b) electrostatic electron-nucleus attraction

c) gravitational attraction between the electron and nucleus

d) magnetic attraction between two neutral particles

40 / 50

40. A hydrogen atom absorbs a photon of energy while initially in the ground state. The final level is closest to

41 / 50

41. Two alpha particles have the same kinetic energy and approach the same nucleus. Particle P has impact parameter , while particle Q has impact parameter . The more strongly deflected particle is

a) neither, because deflection does not depend on

b) particle P

c) both equally

d) particle Q

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42. In the usual notation for an atom, mainly represents

a) the total charge of all electrons

b) protons plus neutrons in the nucleus

c) the radius of the outermost orbit

d) the number of electrons outside the nucleus

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43. In Bohr’s model, radiation is emitted when the electron

a) moves from a lower energy state to a higher energy state by absorbing energy

b) drops from a higher to a lower stationary state

c) remains in the same stationary orbit

d) stays at rest inside the nucleus

44 / 50

44. Match the hydrogen spectral series with its fixed final level.

Column I	Column II
P. Lyman series	1.
Q. Balmer series	2.
R. Paschen series	3.
S. Brackett series	4.

a) P-2, Q-1, R-3, S-4

b) P-2, Q-3, R-1, S-4

c) P-4, Q-3, R-1, S-2

d) P-3, Q-2, R-1, S-4

45 / 50

45. A line in a hydrogen spectrum has the smallest wavelength in the Balmer series. It corresponds to

a) to

b) to

c) to

d) to

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46. In a one-electron ion, an electron in has the same speed as an electron in hydrogen at . The ion’s is

47 / 50

47. A comparison of atomic size and nuclear size is given below.

Region	Typical order of radius
Atom
Nucleus

Based on these values, the ratio is

48 / 50

48. An electron in a Bohr orbit has radius and speed . For a fixed hydrogen-like ion, the product varies as

a) independent of

49 / 50

49. For two hydrogen-like species, the orbit with and the orbit with have radii

a) and , respectively

b) and , respectively

c) and , respectively

d) and , respectively

50 / 50

50. A single hydrogen atom at falls directly to . The emitted photon belongs to the

a) Balmer series

b) Brackett series

c) Lyman series

d) Paschen series

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