Atomic Models MCQ Quiz - Objective Question with Answer for Atomic Models - Download Free PDF

Last updated on Jul 12, 2025

Latest Atomic Models MCQ Objective Questions

Atomic Models Question 1:

Which one of the following particles in the nucleus of an atom was discovered by J. Chadwick?

  1. Electron
  2. Proton
  3. Positron
  4. Neutron

Answer (Detailed Solution Below)

Option 4 : Neutron

Atomic Models Question 1 Detailed Solution

CONCEPT:

Discovery of the Neutron

  • In 1932, James Chadwick discovered the neutron, a subatomic particle present in the nucleus of an atom.
  • The neutron is electrically neutral, meaning it has no charge, and its mass is almost equal to that of a proton.
  • Chadwick's discovery was essential in understanding the atomic nucleus and led to advancements in nuclear physics, including nuclear fission and the development of atomic energy.

EXPLANATION:

  • Before Chadwick's discovery, the nucleus of an atom was thought to consist only of protons.
  • However, the atomic mass of many elements was found to be higher than what could be explained by the number of protons alone.
  • Chadwick conducted experiments by bombarding beryllium with alpha particles, which resulted in the emission of a neutral radiation that could not be explained by existing theories.

He concluded that this radiation consisted of previously unknown particles, which he named neutrons.

Therefore, the particle in the nucleus of an atom discovered by J. Chadwick is the neutron.

Atomic Models Question 2:

Which one of the following statements is correct ?

  1. A neutron is formed by combination of an electron and a proton. Therefore, it is neutral
  2. The mass of an electron is about 1/2000 times that of a proton
  3. An isotope of cobalt is used in the treatment of goiter
  4. J. J. Thomson proposed that the nucleus of an atom contains only neutrons

Answer (Detailed Solution Below)

Option 2 : The mass of an electron is about 1/2000 times that of a proton

Atomic Models Question 2 Detailed Solution

CONCEPT:

Basic Atomic Structure and Properties

  • Atoms are the basic building blocks of matter, consisting of subatomic particles: protons, neutrons, and electrons.
  • Protons are positively charged, electrons are negatively charged, and neutrons are neutral.
  • The mass of an electron is significantly smaller compared to a proton or neutron.
  • Isotopes are variants of an element with the same number of protons but a different number of neutrons.

EXPLANATION:

  • "A neutron is formed by combination of an electron and a proton. Therefore, it is neutral."
    • This statement is incorrect. Neutrons are fundamental particles and are not formed by the combination of a proton and an electron.
  • "The mass of an electron is about 1/2000 times that of a proton."
    • This statement is correct. The mass of an electron is approximately 1/1836 times the mass of a proton, which is close to 1/2000.
  •  "An isotope of cobalt is used in the treatment of goiter."
    • This statement is incorrect. The isotope of iodine, not cobalt, is used in the treatment of goiter.
  • "J. J. Thomson proposed that the nucleus of an atom contains only neutrons."
    • This statement is incorrect. J. J. Thomson proposed the "plum pudding model," and the discovery of the neutron came later by James Chadwick.

Therefore, the correct statement is that the mass of an electron is about 1/2000 times that of a proton.

Atomic Models Question 3:

The Rutherford nuclear model of atom predicts that atoms are unstable because the accelerated electrons revolving around the nucleus must be ______ in the nucleus. 

  1. spiral
  2. elliptical 
  3. circular
  4. linear

Answer (Detailed Solution Below)

Option 1 : spiral

Atomic Models Question 3 Detailed Solution

The correct answer is spiral.

Key Points

  • The Rutherford nuclear model predicts that electrons revolve around the nucleus in orbits due to electrostatic forces.
  • According to classical electromagnetic theory, an accelerating electron would emit radiation, losing energy in the process.
  • This energy loss would cause the electron to spiral inwards towards the nucleus.
  • As the electron spirals inwards, it would eventually collide with the nucleus, leading to the instability of the atom.
  • This instability, predicted by the Rutherford model, contradicts the observed stability of atoms.

Additional Information

  • Rutherford's Nuclear Model
    • Proposed by Ernest Rutherford in 1911 based on the gold foil experiment.
    • Suggested that most of the atom's mass is concentrated in a small, positively charged nucleus.
    • Electrons revolve around this nucleus similar to planets orbiting the sun.
  • Classical Electromagnetic Theory
    • States that any charged particle undergoing acceleration emits electromagnetic radiation.
    • This emission of radiation causes the particle to lose energy.
  • Niels Bohr's Model
    • Proposed in 1913 to address the limitations of Rutherford's model.
    • Introduced the concept of quantized electron orbits where electrons do not radiate energy while in these stable orbits.
  • Quantum Mechanics
    • Further developed the understanding of atomic structure and electron behavior.
    • Explains the stability of atoms through principles such as wave-particle duality and the uncertainty principle.

Atomic Models Question 4:

Which of these models resembles the solar system in which the nucleus plays the role of sun and the electrons that of revolving planets?

  1. Röentgen Model of Atom
  2. Thomson Model of Atom
  3. Bohr’s Model of Atom
  4. Rutherford’s Nuclear Model of Atom 

Answer (Detailed Solution Below)

Option 4 : Rutherford’s Nuclear Model of Atom 

Atomic Models Question 4 Detailed Solution

The correct answer is Rutherford’s Nuclear Model of Atom.

Key Points

  • Rutherford’s Nuclear Model was proposed by Ernest Rutherford in 1911 after his famous gold foil experiment.
  • The model describes the atom as consisting of a dense, positively charged nucleus at the center, surrounded by electrons that revolve in circular paths.
  • It resembles a miniature solar system where the nucleus acts like the sun and electrons behave like planets revolving around the sun.
  • Most of the atom’s mass is concentrated in the nucleus, while the electrons occupy the surrounding space.
  • Rutherford’s model successfully explained the scattering of alpha particles observed in his experiment, disproving the earlier “plum pudding model” proposed by J.J. Thomson.

Additional Information

  • Gold Foil Experiment:
    • Rutherford directed alpha particles at a thin sheet of gold foil to study atomic structure.
    • Most alpha particles passed straight through, but some were deflected at large angles, indicating the presence of a dense nucleus.
  • Limitations of Rutherford’s Model:
    • It could not explain the stability of electrons in circular orbits due to electromagnetic radiation loss.
    • Later, Bohr’s model addressed this limitation by introducing quantized energy levels.
  • Thomson’s Plum Pudding Model:
    • Proposed by J.J. Thomson, it described the atom as a sphere of positive charge with electrons embedded like raisins in a pudding.
    • This model was disproven by Rutherford’s experiment.
  • Comparison with Bohr’s Model:
    • Bohr’s model refined Rutherford’s by proposing quantized orbits for electrons to explain atomic stability and spectral lines.
    • Bohr incorporated Planck’s quantum theory into atomic structure.

Atomic Models Question 5:

How can fast neutrons be slowed down easily?

  1. use of lead shielding 
  2. Passing them through water
  3. Elastic collisions with heavy nuclei 
  4. Applying a strong electric field

Answer (Detailed Solution Below)

Option 2 : Passing them through water

Atomic Models Question 5 Detailed Solution

The Correct answer is Passing them through water.

Key Points

  • Fast neutrons can be slowed down or moderated by passing them through a substance that contains light nuclei.
  • Water is an effective moderator because it contains hydrogen atoms, which have a mass similar to that of neutrons.
  • When fast neutrons collide with the hydrogen nuclei in water, they lose energy through a process called elastic scattering.
  • This reduction in energy slows down the fast neutrons, turning them into slow or thermal neutrons.
  • Slow or thermal neutrons are more likely to induce fission in certain nuclear materials, such as Uranium-235.
  • Water is commonly used in nuclear reactors as both a coolant and a moderator.

 Additional Information

  • Lead shielding
    • Lead is primarily used for its ability to absorb gamma rays and X-rays, not for moderating neutrons.
    • It is not effective in slowing down fast neutrons.
  • Elastic collisions with heavy nuclei
    • Heavy nuclei are less effective in slowing down neutrons compared to light nuclei like hydrogen.
    • Neutrons lose more energy per collision when they collide with light nuclei.
  • Applying a strong electric field
    • Neutrons are neutral particles and are not affected by electric fields.
    • This method would not be effective in slowing down fast neutrons.

Top Atomic Models MCQ Objective Questions

In 1808, whose work provided a physical picture of how compounds are formed by the combination of two or more different types of atoms?

  1. George Zweig
  2. Joseph J Thomson
  3. Niels Bohr
  4. John Dalton

Answer (Detailed Solution Below)

Option 4 : John Dalton

Atomic Models Question 6 Detailed Solution

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The correct answer is John Dalton.
Key Points 
  • John Dalton was an English chemist, physicist, and meteorologist who is best known for his pioneering work in the development of modern atomic theory.
  • Dalton's atomic theory, which he proposed in 1808, provided a physical picture of how compounds are formed by the combination of two or more different types of atoms.
  • He suggested that all matter is made up of tiny, indivisible particles called atoms, which combine in fixed ratios to form compounds.
  • His theory was based on several key principles, including the idea that atoms of different elements have different weights and properties, that atoms can combine to form molecules, and that chemical reactions involve the rearrangement of atoms.
  • Dalton's work on atomic theory was groundbreaking and laid the foundation for modern chemistry.
  • He was also the first scientist to study the behavior of gases and to develop a method for measuring the relative weights of atoms.
Additional Information

George Zweig

  • He proposed the concept of quarks in 1964, which are subatomic particles that makeup protons and neutrons.
  • He suggested that quarks come in six different "flavors" and that they are held together by a strong nuclear force.
  • Joseph J Thomson
  • He discovered the electron in 1897 while studying cathode rays.
  • He proposed the plum pudding model of the atom, which suggested that atoms were made up of a positively charged substance with negatively charged electrons embedded in it.

Niels Bohr

  • He developed the Bohr model of the atom in 1913, which proposed that electrons orbit the nucleus at fixed energy levels.
  • He also suggested that electrons can jump between energy levels by absorbing or emitting energy in the form of photons.

Which one of the following particles in the nucleus of an atom was discovered by J. Chadwick?

  1. Electron
  2. Proton
  3. Positron
  4. Neutron

Answer (Detailed Solution Below)

Option 4 : Neutron

Atomic Models Question 7 Detailed Solution

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CONCEPT:

Discovery of the Neutron

  • In 1932, James Chadwick discovered the neutron, a subatomic particle present in the nucleus of an atom.
  • The neutron is electrically neutral, meaning it has no charge, and its mass is almost equal to that of a proton.
  • Chadwick's discovery was essential in understanding the atomic nucleus and led to advancements in nuclear physics, including nuclear fission and the development of atomic energy.

EXPLANATION:

  • Before Chadwick's discovery, the nucleus of an atom was thought to consist only of protons.
  • However, the atomic mass of many elements was found to be higher than what could be explained by the number of protons alone.
  • Chadwick conducted experiments by bombarding beryllium with alpha particles, which resulted in the emission of a neutral radiation that could not be explained by existing theories.

He concluded that this radiation consisted of previously unknown particles, which he named neutrons.

Therefore, the particle in the nucleus of an atom discovered by J. Chadwick is the neutron.

Which of the following was discovered by Rutherford’s gold foil experiment?  

  1. Neutron 
  2. Nucleus
  3. Electron 
  4. Proton 

Answer (Detailed Solution Below)

Option 2 : Nucleus

Atomic Models Question 8 Detailed Solution

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The Correct answer is Nucleus.

Key Points

  • The gold foil experiment was conducted by Ernest Rutherford in 1909.
  • This experiment involved the bombardment of gold foil with alpha particles.
  • Rutherford observed that most of the alpha particles passed through the foil, but some were deflected at large angles.
  • He concluded that atoms have a small, dense, positively charged center which he called the nucleus.
  • Rutherford's findings significantly changed the atomic model from J.J. Thomson's plum pudding model to the nuclear model.
  • The discovery of the nucleus led to a better understanding of the structure of the atom and the nature of atomic interactions.

 Additional Information

  • Neutron
    • The neutron was discovered by James Chadwick in 1932.
    • It is a neutral particle found in the nucleus of an atom.
    • Neutrons play a crucial role in the stability of the nucleus.
  • Electron
    • The electron was discovered by J.J. Thomson in 1897.
    • Electrons are negatively charged particles that orbit the nucleus of an atom.
    • They are essential in chemical bonding and electricity.
  • Proton
    • The proton was discovered by Ernest Rutherford in 1917.
    • Protons are positively charged particles found in the nucleus of an atom.
    • The number of protons in the nucleus determines the atomic number and identity of an element.

The Rutherford nuclear model of atom predicts that atoms are unstable because the accelerated electrons revolving around the nucleus must be ______ in the nucleus. 

  1. spiral
  2. elliptical 
  3. circular
  4. linear

Answer (Detailed Solution Below)

Option 1 : spiral

Atomic Models Question 9 Detailed Solution

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The correct answer is spiral.

Key Points

  • The Rutherford nuclear model predicts that electrons revolve around the nucleus in orbits due to electrostatic forces.
  • According to classical electromagnetic theory, an accelerating electron would emit radiation, losing energy in the process.
  • This energy loss would cause the electron to spiral inwards towards the nucleus.
  • As the electron spirals inwards, it would eventually collide with the nucleus, leading to the instability of the atom.
  • This instability, predicted by the Rutherford model, contradicts the observed stability of atoms.

Additional Information

  • Rutherford's Nuclear Model
    • Proposed by Ernest Rutherford in 1911 based on the gold foil experiment.
    • Suggested that most of the atom's mass is concentrated in a small, positively charged nucleus.
    • Electrons revolve around this nucleus similar to planets orbiting the sun.
  • Classical Electromagnetic Theory
    • States that any charged particle undergoing acceleration emits electromagnetic radiation.
    • This emission of radiation causes the particle to lose energy.
  • Niels Bohr's Model
    • Proposed in 1913 to address the limitations of Rutherford's model.
    • Introduced the concept of quantized electron orbits where electrons do not radiate energy while in these stable orbits.
  • Quantum Mechanics
    • Further developed the understanding of atomic structure and electron behavior.
    • Explains the stability of atoms through principles such as wave-particle duality and the uncertainty principle.

In order to put up Rutherford's model, what type of metal foil did the scientist use?

  1. Gold
  2. Palladium
  3. Silver
  4. Platinum

Answer (Detailed Solution Below)

Option 1 : Gold

Atomic Models Question 10 Detailed Solution

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The correct answer is Gold.

Key Points

  • Rutherford's model of the atom was developed using a gold foil experiment.
  • The experiment was conducted by Hans Geiger and Ernest Marsden under the supervision of Ernest Rutherford in 1909.
  • Gold was chosen because it is highly malleable, allowing it to be hammered into very thin sheets.
  • The thin gold foil was used to observe the scattering of alpha particles to infer the structure of the atom.
  • This experiment led to the discovery of the atomic nucleus.

Additional Information

  • Alpha Particles:
    • Alpha particles are positively charged particles consisting of two protons and two neutrons.
    • They are emitted during the radioactive decay of certain elements like uranium and radium.
  • Scattering Experiment:
    • In the gold foil experiment, alpha particles were directed at a thin sheet of gold.
    • Most particles passed through, but some were deflected at large angles, indicating a dense, positively charged nucleus.
  • Rutherford's Atomic Model:
    • The model proposed that atoms consist of a small, dense nucleus surrounded by orbiting electrons.
    • This nucleus contains most of the atom's mass and all of its positive charge.
  • Malleability of Gold:
    • Gold's malleability allows it to be hammered into extremely thin sheets, essential for the experiment's success.
    • Its durability and resistance to tarnish make gold ideal for experimental use.

According to Thomson's model of an atom, an atom is compared to which of the following fruits? 

  1. Apple  
  2. Banana 
  3. Watermelon  
  4. Mango 

Answer (Detailed Solution Below)

Option 3 : Watermelon  

Atomic Models Question 11 Detailed Solution

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The correct answer is Watermelon.

Key Points

  • Thomson's model of an atom is often referred to as the "plum pudding model".
  • In this model, the atom is envisioned as a sphere of positive charge.
  • Electrons are embedded within this sphere, similar to seeds in a watermelon.
  • This model was proposed by J.J. Thomson in 1904.

Additional Information

  • J.J. Thomson
    • He was a British physicist who discovered the electron in 1897.
    • He was awarded the Nobel Prize in Physics in 1906 for his work on the conduction of electricity in gases.
  • Plum Pudding Model
    • It represents the atom as a ball of positive charge with electrons scattered throughout.
    • This model was an attempt to explain the structure of the atom after the discovery of the electron.
  • Rutherford's Model
    • Proposed by Ernest Rutherford in 1911, it replaced Thomson's model.
    • According to Rutherford, the atom has a small, dense, positively charged nucleus with electrons orbiting around it.
  • Electron
    • An electron is a subatomic particle with a negative electric charge.
    • It is one of the primary components of an atom, alongside protons and neutrons.

According to the Bohr's model, what is the maximum number of electrons for the second energy level?

  1. 6
  2. 4
  3. 8
  4. 2

Answer (Detailed Solution Below)

Option 3 : 8

Atomic Models Question 12 Detailed Solution

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The correct answer is 8.

Key Points

  • According to the Bohr model, the second energy level can hold a maximum of 8 electrons.
  • Electrons in an atom are arranged in energy levels or shells, which are denoted by the principal quantum number (n).
  • The formula to determine the maximum number of electrons in a shell is given by 2n2, where n is the principal quantum number.
  • For the second energy level (n=2), the maximum number of electrons is calculated as 2(2)2 = 8.
  • This concept is foundational to understanding the electron configuration of atoms and their chemical properties.

Additional Information

  • Principal Quantum Number (n)
    • It denotes the energy level of an electron within an atom.
    • The value of n determines the size and energy of the orbital.
    • Higher values of n correspond to higher energy levels and larger orbitals.
  • Bohr Model
    • Proposed by Niels Bohr in 1913, it describes electrons orbiting the nucleus in fixed energy levels.
    • Electrons can jump between energy levels by absorbing or emitting specific amounts of energy.
    • The model helped explain the spectral lines of hydrogen.
  • Electron Configuration
    • It describes the distribution of electrons in the different energy levels or orbitals of an atom.
    • It follows a specific order based on the Aufbau principle, Pauli exclusion principle, and Hund's rule.
    • Electron configuration helps predict chemical behavior and bonding.
  • Aufbau Principle
    • It states that electrons fill lower energy orbitals first before moving to higher energy orbitals.
    • This principle guides the order in which atomic orbitals are filled.

How can fast neutrons be slowed down easily?

  1. use of lead shielding 
  2. Passing them through water
  3. Elastic collisions with heavy nuclei 
  4. Applying a strong electric field

Answer (Detailed Solution Below)

Option 2 : Passing them through water

Atomic Models Question 13 Detailed Solution

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The Correct answer is Passing them through water.

Key Points

  • Fast neutrons can be slowed down or moderated by passing them through a substance that contains light nuclei.
  • Water is an effective moderator because it contains hydrogen atoms, which have a mass similar to that of neutrons.
  • When fast neutrons collide with the hydrogen nuclei in water, they lose energy through a process called elastic scattering.
  • This reduction in energy slows down the fast neutrons, turning them into slow or thermal neutrons.
  • Slow or thermal neutrons are more likely to induce fission in certain nuclear materials, such as Uranium-235.
  • Water is commonly used in nuclear reactors as both a coolant and a moderator.

 Additional Information

  • Lead shielding
    • Lead is primarily used for its ability to absorb gamma rays and X-rays, not for moderating neutrons.
    • It is not effective in slowing down fast neutrons.
  • Elastic collisions with heavy nuclei
    • Heavy nuclei are less effective in slowing down neutrons compared to light nuclei like hydrogen.
    • Neutrons lose more energy per collision when they collide with light nuclei.
  • Applying a strong electric field
    • Neutrons are neutral particles and are not affected by electric fields.
    • This method would not be effective in slowing down fast neutrons.

Which one of the following statements is correct ?

  1. A neutron is formed by combination of an electron and a proton. Therefore, it is neutral
  2. The mass of an electron is about 1/2000 times that of a proton
  3. An isotope of cobalt is used in the treatment of goiter
  4. J. J. Thomson proposed that the nucleus of an atom contains only neutrons

Answer (Detailed Solution Below)

Option 2 : The mass of an electron is about 1/2000 times that of a proton

Atomic Models Question 14 Detailed Solution

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CONCEPT:

Basic Atomic Structure and Properties

  • Atoms are the basic building blocks of matter, consisting of subatomic particles: protons, neutrons, and electrons.
  • Protons are positively charged, electrons are negatively charged, and neutrons are neutral.
  • The mass of an electron is significantly smaller compared to a proton or neutron.
  • Isotopes are variants of an element with the same number of protons but a different number of neutrons.

EXPLANATION:

  • "A neutron is formed by combination of an electron and a proton. Therefore, it is neutral."
    • This statement is incorrect. Neutrons are fundamental particles and are not formed by the combination of a proton and an electron.
  • "The mass of an electron is about 1/2000 times that of a proton."
    • This statement is correct. The mass of an electron is approximately 1/1836 times the mass of a proton, which is close to 1/2000.
  •  "An isotope of cobalt is used in the treatment of goiter."
    • This statement is incorrect. The isotope of iodine, not cobalt, is used in the treatment of goiter.
  • "J. J. Thomson proposed that the nucleus of an atom contains only neutrons."
    • This statement is incorrect. J. J. Thomson proposed the "plum pudding model," and the discovery of the neutron came later by James Chadwick.

Therefore, the correct statement is that the mass of an electron is about 1/2000 times that of a proton.

Which of these models resembles the solar system in which the nucleus plays the role of sun and the electrons that of revolving planets?

  1. Röentgen Model of Atom
  2. Thomson Model of Atom
  3. Bohr’s Model of Atom
  4. Rutherford’s Nuclear Model of Atom 

Answer (Detailed Solution Below)

Option 4 : Rutherford’s Nuclear Model of Atom 

Atomic Models Question 15 Detailed Solution

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The correct answer is Rutherford’s Nuclear Model of Atom.

Key Points

  • Rutherford’s Nuclear Model was proposed by Ernest Rutherford in 1911 after his famous gold foil experiment.
  • The model describes the atom as consisting of a dense, positively charged nucleus at the center, surrounded by electrons that revolve in circular paths.
  • It resembles a miniature solar system where the nucleus acts like the sun and electrons behave like planets revolving around the sun.
  • Most of the atom’s mass is concentrated in the nucleus, while the electrons occupy the surrounding space.
  • Rutherford’s model successfully explained the scattering of alpha particles observed in his experiment, disproving the earlier “plum pudding model” proposed by J.J. Thomson.

Additional Information

  • Gold Foil Experiment:
    • Rutherford directed alpha particles at a thin sheet of gold foil to study atomic structure.
    • Most alpha particles passed straight through, but some were deflected at large angles, indicating the presence of a dense nucleus.
  • Limitations of Rutherford’s Model:
    • It could not explain the stability of electrons in circular orbits due to electromagnetic radiation loss.
    • Later, Bohr’s model addressed this limitation by introducing quantized energy levels.
  • Thomson’s Plum Pudding Model:
    • Proposed by J.J. Thomson, it described the atom as a sphere of positive charge with electrons embedded like raisins in a pudding.
    • This model was disproven by Rutherford’s experiment.
  • Comparison with Bohr’s Model:
    • Bohr’s model refined Rutherford’s by proposing quantized orbits for electrons to explain atomic stability and spectral lines.
    • Bohr incorporated Planck’s quantum theory into atomic structure.
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