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
Retake: Until certificate earned
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Atoms – Progressive Test

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1 / 50

1. Rutherford’s model and Bohr’s model both include

a) no charged particles inside the atom

b) electrons embedded motionlessly in a positive sphere

c) a central positive nucleus with electrons outside it

d) positive charge spread uniformly through the whole atom

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2. A student applies to neutral lithium. The main mistake is that neutral lithium is

a) not a one-electron system

b) unable to absorb radiation

c) a nucleus-free atom

d) identical to

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3. Use the energy-level description below.

For hydrogen, , , , and . A photon of energy is emitted by a downward transition.

The transition is

4 / 50

4. Bohr’s radius formula and speed formula show opposite dependences on because

a) both and are independent of

b) , while for fixed

c) both and are proportional to

d) , while for fixed

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

a) four times as large

b) twice as large

c) half as large

d) the same

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6. Consider the two statements below.
I. Thomson’s model could explain the overall neutrality of an atom.
II. Thomson’s model could explain large-angle alpha-particle scattering by a tiny dense nucleus.

a) Both I and II are true

b) I is true, but II is false

c) I is false, but II is true

d) Both I and II are false

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7. A table lists possible hydrogen processes from the ground state.

Row	Energy supplied	Process stated
P		Excitation to
Q		Excitation to
R		Ionisation with zero kinetic energy
S		Excitation to

The row that needs correction is

a) Row S

b) Row R

c) Row Q

d) Row P

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8. A graph is described below.

The horizontal axis lists successive visible hydrogen lines from red toward violet. The vertical axis shows wavelength. The plotted points decrease in wavelength and get closer together toward a limiting value.

This trend suggests that the hydrogen spectral lines

a) spread farther apart without bound

b) form a continuous spectrum from the first line onward

c) converge toward a series limit

d) have equal wavelength separation forever

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9. A hydrogen atom emits a photon of energy . This photon is incident on another hydrogen atom in . The second atom

a) cannot interact because it is already excited

b) can be ionised with kinetic energy

c) can be excited to

d) can be excited to

10 / 50

10. A graph description is given below.

Two straight-line graphs of versus pass through the origin. Graph P has a larger slope than graph Q.

If both graphs represent hydrogen-like atoms, the graph with the larger slope corresponds to

a) a nucleus with zero charge

b) the larger value of only

c) the smaller value of

d) the larger value of

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11. Use the table below to identify the row that gives the most suitable basic meaning.

Row	Term	Meaning
P		Number of protons in the nucleus
Q		Number of protons plus neutrons
R	Neutral atom	Total positive charge equals total negative charge
S	Photon	A proton inside the nucleus

a) Rows Q, R, and S only

b) Rows P, Q, and R only

c) Row P only

d) Rows P and Q only

12 / 50

12. A graph of versus for a hydrogen-like ion has slope . The value of is

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13. A graph description is given below.

Graph P shows intensity spread smoothly over a continuous range of wavelengths. Graph Q shows intensity only at a few separated wavelengths.

The graph that better represents an atomic line spectrum is

a) Graph Q, because atoms emit or absorb only selected wavelengths

b) Graph P, because atomic energy is always continuous

c) Graph P, because atoms emit all wavelengths equally

d) neither graph, because atoms cannot emit radiation

14 / 50

14. A reason for choosing gold foil in Rutherford’s experiment was that gold

a) converts alpha particles into neutrons

b) has no positive charge in its atoms

c) can be made into extremely thin sheets

d) emits all hydrogen spectral lines

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

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16. In a head-on approach of an -particle toward a positive nucleus, the deflection is maximum because

a) the alpha particle avoids the electric field completely

b) the nucleus attracts the alpha particle at every point

c) the path reaches the strongest repulsion region

d) the alpha particle becomes a photon at closest approach

17 / 50

17. Assertion: Thomson’s model was able to explain the electrical neutrality of atoms.
Reason: In Thomson’s model, electrons were embedded in a sphere of positive charge.

a) Assertion is false, but Reason is true

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

c) Assertion is true, but Reason is false

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

18 / 50

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

19 / 50

19. The stability of Bohr’s atom depends most directly on the idea that

a) the nucleus has no positive charge

b) stationary orbits do not radiate

c) atoms contain no moving particles

d) electrons are not charged particles

20 / 50

20. In an emission spectrum of an atom, bright lines are produced when

a) electrons move from higher energy states to lower energy states and emit photons

b) the nucleus absorbs all visible light without re-emission

c) electrons remain forever in one state while emitting all frequencies

d) electrons absorb photons and move from lower energy states to higher energy states only

21 / 50

21. For the same principal quantum number , the electron speed in compared with hydrogen is

a) one-third as large

b) the same

c) nine times larger

d) three times larger

22 / 50

22. In atomic physics, a photon is best described as

a) a neutron emitted from every atom

b) a proton moving outside the nucleus

c) an electron whose charge has become positive

d) a particle of radiation carrying energy

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23. For a fixed target and fixed scattering angle in Rutherford scattering, increasing the kinetic energy of the incident -particles reduces large-angle scattering mainly because

a) the scattered count decreases with higher

b) the nucleus becomes neutral at high energy

c) the gold foil stops containing atoms

d) the -particle charge changes from to

24 / 50

24. A hydrogen atom emits a photon of frequency . Taking and , the photon energy is closest to

25 / 50

25. For the Balmer first line of hydrogen, and . The wavenumber is

26 / 50

26. The discovery of the electron showed that

a) atomic mass is always zero

b) all atoms are made only of photons

c) atoms have no internal structure

d) atoms contain electrons

27 / 50

27. The main reason Bohr’s model was not just a repetition of Rutherford’s model is that Bohr added

a) the idea that alpha particles are neutral

b) quantised electron motion and radiation

c) the idea that electrons are absent from atoms

d) a uniformly spread positive charge throughout the atom

28 / 50

28. Bohr’s first postulate about stationary orbits was needed because classical theory predicted that a revolving electron should

a) remain stable without any special rule

b) become a neutron

c) radiate energy continuously

d) absorb all photons at every wavelength

29 / 50

29. The kinetic energy of the electron in the Bohr orbit is related to its speed by

30 / 50

30. A claim says, “The zinc sulphide screen was used to scatter alpha particles strongly.” The better correction is that the screen was used to

a) supply the incident alpha beam

b) create the positive nucleus inside gold atoms

c) detect alpha particles after scattering

d) make alpha particles pass undeflected

31 / 50

31. An -particle of kinetic energy has closest approach to a nucleus of charge . Another -particle approaches a nucleus of charge with kinetic energy . The new closest approach is

32 / 50

32. An alpha particle has twice the kinetic energy of another alpha particle. Both approach the same nucleus head-on. If the lower-energy particle has closest approach , the higher-energy particle reaches

a) infinite distance because Coulomb force vanishes near the nucleus

b) exactly the same distance because is independent of energy

c) a smaller distance because it can work further against repulsion

d) a larger distance because it is repelled sooner

33 / 50

33. For a fixed target nucleus, an -particle passing closer to the nucleus suffers a larger deflection mainly because

a) the alpha particle loses its positive charge at small distance

b) gravitational force suddenly becomes zero

c) Coulomb repulsion increases as separation decreases

d) the nucleus changes into an electron at small distance

34 / 50

34. A hydrogen atom is excited to . The maximum number of distinct emission lines possible as atoms in a sample return to lower levels is

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35. A Rutherford atom has nuclear charge and is electrically neutral. The number of extranuclear electrons in it is

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36. For a hydrogen-like ion, the graph of versus has slope . If the slope is , the ion has

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

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38. A hydrogen-like ion means an ion that

a) gives only continuous spectra

b) has exactly one neutron and no proton

c) has only one electron

d) has no nucleus

39 / 50

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

40 / 50

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

a) the number of electrons outside the nucleus

b) the total charge of all electrons

c) the radius of the outermost orbit

d) protons plus neutrons in the nucleus

41 / 50

41. A proposed orbit contains complete de Broglie wavelengths around its circumference. In the Bohr-de Broglie interpretation, the corresponding value of is

42 / 50

42. The gold foil in Rutherford’s experiment had to be very thin so that

a) the foil would remove the positive charge from alpha particles

b) the foil would stop all alpha particles completely

c) alpha particles met only a few atomic layers

d) electrons in the foil would become massless

43 / 50

43. A head-on alpha-scattering case has initial kinetic energy . The target nucleus has charge . The alpha particle has charge . The electrostatic potential energy at closest approach is

44 / 50

44. A passage describes three pieces of evidence.

Observation P: Most alpha particles pass through thin foil almost undeflected. Observation Q: Hydrogen emits separated spectral lines. Observation R: A revolving charged electron should radiate energy by classical theory, yet atoms are stable.

The most suitable model-response pair is

a) P disproves the nucleus, while Q and R support Thomson’s spread-out positive charge

b) P, Q, and R are all fully explained by Thomson’s model alone

c) P needs Rutherford; Q and R need Bohr

d) Q is unrelated to energy levels, while R proves electrons are uncharged

45 / 50

45. In a Bohr orbit, the electron’s angular momentum is , and the orbit radius is . If the atom is hydrogen, the electron speed is

46 / 50

46. The impact parameter in alpha-particle scattering is the

a) distance between the alpha source and the screen

b) perpendicular distance from the nucleus to the initial path

c) radius of the gold atom after scattering

d) distance travelled by the alpha particle after hitting the screen

47 / 50

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

Level	Energy

The ionisation energy from is

48 / 50

48. A hydrogen atom emits a photon when its electron moves from to . Using and , the photon energy is closest to

49 / 50

49. A graph is described below.

The horizontal axis shows scattering angle , starting from small angles and moving toward large angles. The vertical axis shows the number of -particles detected at that angle.

The graph expected from Rutherford’s observations would show

a) a large count at small angles and a very small count at large angles

b) the same count at every scattering angle

c) no detected particles at any angle

d) zero count at small angles and maximum count at backscattering angles

50 / 50

50. Study the table about de Broglie and Bohr quantisation.

Row	Statement	Status
P		de Broglie wavelength relation
Q		standing-wave condition for allowed circular orbit
R		Bohr angular momentum condition
S		allowed standing wave with

The row that needs correction is

a) Row Q

b) Row S

c) Row R

d) Row P

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