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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The Correct answer is K, L, M, N, O...

Key Points

• Niels Bohr, in his atomic model, represented different electron orbits or energy levels using the symbols K, L, M, N, O....
• These orbits correspond to the principal quantum numbers (n = 1, 2, 3, 4, 5...) and represent specific energy levels around the nucleus.
• Each orbit is associated with a specific energy state, with the K-shell (n=1) being the closest to the nucleus and having the lowest energy.
• This representation helped in understanding the distribution of electrons in an atom and their arrangement across various energy levels.
• The concept of energy levels (or shells) is crucial in explaining the chemical properties of elements and the formation of bonds.
• The naming convention (K, L, M, N...) was adopted to avoid confusion with the alphabetical representation of other atomic properties like subshells (s, p, d, f).
• This model laid the foundation for the modern quantum mechanical model of the atom.

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.

The correct answer is 1000 atomsKey Points

• Ernest Rutherford used a gold foil that was about 1,000 atoms thick for his alpha scattering experiment. 
• Rutherford chose gold because it is malleable, which allowed him to make a very thin sheet of the metal.
• He wanted to use the thinnest layer of metal possible so that he could get clear observations.
• Using a different metal would not have produced accurate results. 
• In the experiment, Rutherford shot high-energy alpha particles at the gold foil and observed how the particles deflected.
• He placed a fluorescent zinc sulfide screen around the foil to study the deflection.
• The experiment led to the discovery of the nucleus and contradicted Thomson's atomic model.