In the Bohr model of the hydrogen atom, the total energy of an electron in any allowed orbit has a negative value. What is the physical significance of this negative total energy?

A) It indicates that the negative electric charge of the electron exceeds the positive charge of the nucleus.

B) It means that the kinetic energy of the orbiting electron exceeds the magnitude of its potential energy.

C) It indicates that the electron is bound to the nucleus, requiring an input of energy to be freed.

D) It implies that the electrostatic force acting on the electron is repulsive rather than attractive.

What was the primary significance of Robert Millikan's oil drop experiment in the development of atomic theory?

A) It demonstrated that electrons occupy quantized, discrete energy levels around the nucleus.

B) It revealed that an atom's positive charge is concentrated in a dense central nucleus.

C) It determined the fundamental electric charge of the electron, enabling the calculation of its mass.

D) It provided evidence that atomic nuclei contain electrically neutral particles called neutrons.

In his cathode ray tube experiments, which physical property of the electron was J. J. Thomson able to determine experimentally?

A) The fundamental electric charge of an individual electron

B) The ratio of the electron's electric charge to its mass

C) The absolute rest mass of an individual electron

D) The precise physical radius of an individual electron

According to Louis de Broglie's wave interpretation of the Bohr model, which condition must be satisfied for an electron to maintain a stable, non-radiating orbit?

A) The radius of the orbit must equal an integer multiple of the electron's de Broglie wavelength.

B) The speed of the electron must be an integer fraction of the speed of light in a vacuum.

C) The circumference of the orbit must be an integer multiple of the electron's de Broglie wavelength.

D) The kinetic energy of the electron must equal the photon energy required for ionization.

According to Niels Bohr's model of the hydrogen atom, how does the radius of an allowed orbit depend on the principal quantum number $n$?

A) It is inversely proportional to $n$.

B) It is directly proportional to $n$.

C) It is directly proportional to $n^2$.

D) It is inversely proportional to $n^2$.

In Ernest Rutherford's planetary model of the atom, which force provides the centripetal acceleration required to keep electrons in orbit around the nucleus?

A) The electrostatic attraction between the positively charged nucleus and the negatively charged electrons

B) The gravitational attraction between the massive central nucleus and the orbiting electrons

C) The strong nuclear force acting across the empty space of the atom

D) The magnetic force produced by the orbital motion of the charged particles

Based on J. J. Thomson's plum pudding model of the atom, what was expected to happen when alpha particles were directed at a thin gold foil?

A) The alpha particles would be absorbed by the diffuse positive sphere of the atoms.

B) The alpha particles would pass through the foil with only negligible deflections.

C) A significant portion of the alpha particles would be reflected backward toward the source.

D) The alpha particles would strip electrons from the atoms and be stopped completely.

Which discovery provided the first direct experimental evidence disproving John Dalton's postulate that atoms are indivisible particles?

A) The discovery that atoms of the same element can exist as isotopes with different masses

B) The detection of the electrically neutral neutron inside the atomic nucleus

C) The identification of the electron as a subatomic constituent of cathode rays

D) The observation of large-angle alpha particle scattering by thin gold foil

Which of the following describes a major limitation of the Bohr model of the atom?

A) It failed to account for the presence of a dense, positively charged nucleus.

B) It could not explain why alpha particles pass through thin metal foils undeflected.

C) It was unable to accurately predict the emission spectra of atoms containing more than one electron.

D) It incorrectly treated electrons as continuous positively charged matter embedding negative particles.

Which major discovery in 1932 resolved the discrepancy between an atom's nuclear charge and its total atomic mass, thereby completing the nuclear model of the atom?

A) James Chadwick's discovery of the electrically neutral neutron residing in the nucleus.

B) Robert Millikan's determination of the fundamental electric charge carried by an electron.

C) J. J. Thomson's measurement of the charge-to-mass ratio of the cathode-ray electron.

D) Louis de Broglie's proposal of wave-particle duality for orbiting atomic electrons.

In his cathode ray tube experiments, which observation led J. J. Thomson to conclude that the negatively charged particles (electrons) are universal constituents of all matter?

A) The measured charge-to-mass ratio of the particles remained constant regardless of the metal used for the cathode or the residual gas in the tube.

B) The particles traveled in straight lines and were deflected only by strong magnetic fields while remaining completely unaffected by electrostatic plates.

C) The velocity of the emitted particles was found to be strictly equal to the speed of light regardless of the accelerating voltage applied.

D) The mass of an individual cathode ray particle was calculated to be equal to the mass of an intact neutral hydrogen atom.

In Niels Bohr's atomic model, how is the emission of light at discrete wavelengths by excited hydrogen atoms explained?

A) Electrons are ejected entirely from the atom, converting their remaining kinetic energy into radiant electromagnetic waves.

B) Protons in the nucleus vibrate at characteristic harmonic frequencies and emit electromagnetic radiation directly.

C) Electrons transition from higher discrete energy levels to lower discrete energy levels, releasing photons with energies equal to the difference between these states.

D) Continuous centripetal acceleration of electrons within a single orbit continuously sheds energy as radiation.

According to John Dalton's atomic theory, what occurs to atoms during a chemical reaction?

A) Atoms of one element are transmuted into atoms of a different element.

B) Atoms gain, lose, or share valence electrons to achieve stable configurations.

C) Atoms are combined, separated, or rearranged without being created or destroyed.

D) Atoms decompose into fundamental subatomic particles that reassemble into new substances.

Which statement correctly describes how the modern quantum mechanical model of the atom represents the behavior of electrons?

A) Electrons travel along fixed, predetermined circular paths around the nucleus at constant speeds.

B) Electrons are embedded statically throughout a positively charged spherical matrix.

C) Electrons occupy three-dimensional regions of space called orbitals, where the probability of finding them is high.

D) Electrons are confined entirely within the atomic nucleus and escape only during nuclear reactions.

Which postulate of John Dalton's atomic theory was directly contradicted by the subsequent discovery of isotopes?

A) All atoms of a given element possess identical masses and properties.

B) Compounds are formed when atoms of different elements combine in fixed, whole-number ratios.

C) Chemical reactions involve the rearrangement of atoms without creating or destroying them.

D) Atoms of different elements have distinctly different chemical properties and masses.

According to Niels Bohr's atomic model, which statement explains why an orbiting electron does not continuously emit electromagnetic radiation and collapse into the nucleus?

A) The electrostatic attraction of the nucleus is entirely balanced by a repulsive magnetic field generated by the electron.

B) The electron continuously absorbs radiation from the surrounding space to replenish its orbital energy.

C) The electron moves with a constant linear velocity that eliminates centripetal acceleration.

D) The electron is restricted to discrete stationary orbits in which it revolves without radiating energy.

Which statement correctly describes the distribution of electric charge in J. J. Thomson's atomic model?

A) Electrons orbit a small, positively charged central nucleus in fixed circular paths.

B) Negatively charged electrons are embedded throughout a continuous sphere of positive charge.

C) Positive and negative charges are concentrated entirely within a dense central core surrounded by empty space.

D) Positively charged protons orbit a massive central core made of stationary negative charge.

Which conclusion was directly drawn by Ernest Rutherford from the observation that a tiny fraction of alpha particles were deflected at very large angles during the gold foil experiment?

A) Electrons are embedded uniformly within a continuous sphere of positive charge.

B) The positive charge and most of the atom's mass are concentrated in a tiny, dense nucleus.

C) Electrons can only occupy discrete energy levels without radiating electromagnetic energy.

D) Atoms are indivisible and indestructible solid spheres that combine in fixed whole-number ratios.

Atomic models Knowledge-Based Download PDF

Physics · Matter · Physics · Properties & States of Matter

20 Physics practice questions on Atomic models. Questions that assess core concepts and understanding.

Questions

1.
In the emission spectrum of atomic hydrogen, which spectral series is produced by electron transitions that terminate at the ground state (n = 1)?
- A) Lyman series
- B) Balmer series
- C) Paschen series
- D) Brackett series
2.
In the Bohr model of the hydrogen atom, the total energy of an electron in any allowed orbit has a negative value. What is the physical significance of this negative total energy?
- A) It indicates that the negative electric charge of the electron exceeds the positive charge of the nucleus.
- B) It means that the kinetic energy of the orbiting electron exceeds the magnitude of its potential energy.
- C) It indicates that the electron is bound to the nucleus, requiring an input of energy to be freed.
- D) It implies that the electrostatic force acting on the electron is repulsive rather than attractive.
3.
What was the primary significance of Robert Millikan's oil drop experiment in the development of atomic theory?
- A) It demonstrated that electrons occupy quantized, discrete energy levels around the nucleus.
- B) It revealed that an atom's positive charge is concentrated in a dense central nucleus.
- C) It determined the fundamental electric charge of the electron, enabling the calculation of its mass.
- D) It provided evidence that atomic nuclei contain electrically neutral particles called neutrons.
4.
In his cathode ray tube experiments, which physical property of the electron was J. J. Thomson able to determine experimentally?
- A) The fundamental electric charge of an individual electron
- B) The ratio of the electron's electric charge to its mass
- C) The absolute rest mass of an individual electron
- D) The precise physical radius of an individual electron
5.
According to Louis de Broglie's wave interpretation of the Bohr model, which condition must be satisfied for an electron to maintain a stable, non-radiating orbit?
- A) The radius of the orbit must equal an integer multiple of the electron's de Broglie wavelength.
- B) The speed of the electron must be an integer fraction of the speed of light in a vacuum.
- C) The circumference of the orbit must be an integer multiple of the electron's de Broglie wavelength.
- D) The kinetic energy of the electron must equal the photon energy required for ionization.
6.
According to Niels Bohr's model of the hydrogen atom, how does the radius of an allowed orbit depend on the principal quantum number $n$ ?
- A) It is inversely proportional to $n$ .
- B) It is directly proportional to $n$ .
- C) It is directly proportional to $n^2$ .
- D) It is inversely proportional to $n^2$ .
7.
In Ernest Rutherford's planetary model of the atom, which force provides the centripetal acceleration required to keep electrons in orbit around the nucleus?
- A) The electrostatic attraction between the positively charged nucleus and the negatively charged electrons
- B) The gravitational attraction between the massive central nucleus and the orbiting electrons
- C) The strong nuclear force acting across the empty space of the atom
- D) The magnetic force produced by the orbital motion of the charged particles
8.
Based on J. J. Thomson's plum pudding model of the atom, what was expected to happen when alpha particles were directed at a thin gold foil?
- A) The alpha particles would be absorbed by the diffuse positive sphere of the atoms.
- B) The alpha particles would pass through the foil with only negligible deflections.
- C) A significant portion of the alpha particles would be reflected backward toward the source.
- D) The alpha particles would strip electrons from the atoms and be stopped completely.
9.
In Niels Bohr's atomic model, which physical quantity of an electron is postulated to be an integer multiple of $h / (2\pi)$ ?
- A) Total mechanical energy
- B) Orbital angular momentum
- C) Linear momentum
- D) Electric potential energy
10.
Which discovery provided the first direct experimental evidence disproving John Dalton's postulate that atoms are indivisible particles?
- A) The discovery that atoms of the same element can exist as isotopes with different masses
- B) The detection of the electrically neutral neutron inside the atomic nucleus
- C) The identification of the electron as a subatomic constituent of cathode rays
- D) The observation of large-angle alpha particle scattering by thin gold foil
11.
Which of the following describes a major limitation of the Bohr model of the atom?
- A) It failed to account for the presence of a dense, positively charged nucleus.
- B) It could not explain why alpha particles pass through thin metal foils undeflected.
- C) It was unable to accurately predict the emission spectra of atoms containing more than one electron.
- D) It incorrectly treated electrons as continuous positively charged matter embedding negative particles.
12.
Which major discovery in 1932 resolved the discrepancy between an atom's nuclear charge and its total atomic mass, thereby completing the nuclear model of the atom?
- A) James Chadwick's discovery of the electrically neutral neutron residing in the nucleus.
- B) Robert Millikan's determination of the fundamental electric charge carried by an electron.
- C) J. J. Thomson's measurement of the charge-to-mass ratio of the cathode-ray electron.
- D) Louis de Broglie's proposal of wave-particle duality for orbiting atomic electrons.
13.
In his cathode ray tube experiments, which observation led J. J. Thomson to conclude that the negatively charged particles (electrons) are universal constituents of all matter?
- A) The measured charge-to-mass ratio of the particles remained constant regardless of the metal used for the cathode or the residual gas in the tube.
- B) The particles traveled in straight lines and were deflected only by strong magnetic fields while remaining completely unaffected by electrostatic plates.
- C) The velocity of the emitted particles was found to be strictly equal to the speed of light regardless of the accelerating voltage applied.
- D) The mass of an individual cathode ray particle was calculated to be equal to the mass of an intact neutral hydrogen atom.
14.
In Niels Bohr's atomic model, how is the emission of light at discrete wavelengths by excited hydrogen atoms explained?
- A) Electrons are ejected entirely from the atom, converting their remaining kinetic energy into radiant electromagnetic waves.
- B) Protons in the nucleus vibrate at characteristic harmonic frequencies and emit electromagnetic radiation directly.
- C) Electrons transition from higher discrete energy levels to lower discrete energy levels, releasing photons with energies equal to the difference between these states.
- D) Continuous centripetal acceleration of electrons within a single orbit continuously sheds energy as radiation.
15.
According to John Dalton's atomic theory, what occurs to atoms during a chemical reaction?
- A) Atoms of one element are transmuted into atoms of a different element.
- B) Atoms gain, lose, or share valence electrons to achieve stable configurations.
- C) Atoms are combined, separated, or rearranged without being created or destroyed.
- D) Atoms decompose into fundamental subatomic particles that reassemble into new substances.
16.
Which statement correctly describes how the modern quantum mechanical model of the atom represents the behavior of electrons?
- A) Electrons travel along fixed, predetermined circular paths around the nucleus at constant speeds.
- B) Electrons are embedded statically throughout a positively charged spherical matrix.
- C) Electrons occupy three-dimensional regions of space called orbitals, where the probability of finding them is high.
- D) Electrons are confined entirely within the atomic nucleus and escape only during nuclear reactions.
17.
Which postulate of John Dalton's atomic theory was directly contradicted by the subsequent discovery of isotopes?
- A) All atoms of a given element possess identical masses and properties.
- B) Compounds are formed when atoms of different elements combine in fixed, whole-number ratios.
- C) Chemical reactions involve the rearrangement of atoms without creating or destroying them.
- D) Atoms of different elements have distinctly different chemical properties and masses.
18.
According to Niels Bohr's atomic model, which statement explains why an orbiting electron does not continuously emit electromagnetic radiation and collapse into the nucleus?
- A) The electrostatic attraction of the nucleus is entirely balanced by a repulsive magnetic field generated by the electron.
- B) The electron continuously absorbs radiation from the surrounding space to replenish its orbital energy.
- C) The electron moves with a constant linear velocity that eliminates centripetal acceleration.
- D) The electron is restricted to discrete stationary orbits in which it revolves without radiating energy.
19.
Which statement correctly describes the distribution of electric charge in J. J. Thomson's atomic model?
- A) Electrons orbit a small, positively charged central nucleus in fixed circular paths.
- B) Negatively charged electrons are embedded throughout a continuous sphere of positive charge.
- C) Positive and negative charges are concentrated entirely within a dense central core surrounded by empty space.
- D) Positively charged protons orbit a massive central core made of stationary negative charge.
20.
Which conclusion was directly drawn by Ernest Rutherford from the observation that a tiny fraction of alpha particles were deflected at very large angles during the gold foil experiment?
- A) Electrons are embedded uniformly within a continuous sphere of positive charge.
- B) The positive charge and most of the atom's mass are concentrated in a tiny, dense nucleus.
- C) Electrons can only occupy discrete energy levels without radiating electromagnetic energy.
- D) Atoms are indivisible and indestructible solid spheres that combine in fixed whole-number ratios.

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