Structure of Atom Class 11 MCQ

Correct Answer: C. Indian and Greek philosophers, around 400 B.C., first proposed atoms as fundamental building blocks of matter.

Correct Answer: A. The word ‘atom’ is derived from the Greek word ‘a-tomio,’ meaning ‘indivisible’ or ‘uncut-able.’

Correct Answer: B. John Dalton proposed the atomic theory on a firm scientific basis in 1808.

Correct Answer: D. Dalton’s theory explained the Law of Conservation of Mass, the Law of Multiple Proportions, and the Law of Constant Composition.

Correct Answer: C. The Law of Conservation of Mass states that matter cannot be created or destroyed in a chemical reaction.

Correct Answer: C. The Law of Constant Composition is based on this observation.

Correct Answer: A. The Law of Multiple Proportions states that elements can form more than one compound in different proportions.

Correct Answer: B. Dalton’s atomic theory could not explain the behavior of electrically charged substances like glass or ebonite when rubbed with silk or fur.

Correct Answer: C. Michael Faraday showed this phenomenon in 1830.

Correct Answer: B. The Cathode Ray Discharge Tube experiment led to the discovery of cathode rays.

Correct Answer: C. Cathode rays originate from the cathode and move towards the anode.

Correct Answer: A. The cathode ray experiment showed that atoms are made up of subatomic particles, specifically electrons.

Correct Answer: B. Thomson discovered the charge to mass ratio of the electron using the Cathode Ray Tube Experiment.

Correct Answer: A. The charge to mass ratio of the electron is $1.758820 \times 10^{11}$ C kg⁻¹.

Correct Answer: D. The charge of the positive electrode does not directly influence the deflection of electrons.

Correct Answer: C. R.A. Millikan determined the charge on the electron using the oil drop experiment.

Correct Answer: B. The charge on the electron is –$1.602176 \times 10^{-19}$ C.

Correct Answer: A. The mass of the electron is $9.1094 \times 10^{-31}$ kg.

Correct Answer: C. Protons were first observed in experiments involving canal rays.

Correct Answer: A. The mass of a proton is approximately 2000 times greater than that of an electron.

Correct Answer: C. James Chadwick discovered the neutron in 1932.

Correct Answer: C. Neutrons were discovered by bombarding a thin sheet of beryllium with alpha particles.

Correct Answer: B. Protons have a mass similar to that of neutrons.

Correct Answer: C. Protons were first characterized as positively charged particles in 1919.

Correct Answer: C. Neutrons have no charge and a mass slightly greater than that of protons.

Correct Answer: D. The Canal Ray Experiment led to the discovery of positively charged particles (protons).

Correct Answer: A. Thomson’s Plum Pudding Model describes the atom as a sphere of positive charge with electrons scattered inside.

Correct Answer: B. Thomson’s model failed to explain the results of later experiments, like Rutherford’s scattering experiment.

Correct Answer: C. Thomson’s model visualizes the atom as a positively charged pudding with negative electrons embedded.

Correct Answer: B. Rutherford’s Gold Foil Experiment led to the eventual discrediting of Thomson’s Plum Pudding Model.

Correct Answer: B. Rutherford’s Nuclear Model was based on the Gold Foil Experiment.

Correct Answer: A. Most alpha particles passed through the foil with no deflection, suggesting that most of the atom is empty space.

Correct Answer: A. Rutherford concluded that atoms consist mainly of empty space, with a small, dense nucleus.

Correct Answer: C. The nucleus is described as small, dense, and positively charged.

Correct Answer: B. Rutherford’s experiment did not lead to the discovery of neutrons; they were discovered later by Chadwick.

Correct Answer: B. Rutherford’s model was unable to explain the arrangement of electrons around the nucleus.

Correct Answer: B. Rutherford’s model resembles the solar system, with the nucleus as the Sun and electrons revolving like planets.

Correct Answer: B. The atomic number is defined as the number of protons in the nucleus of an atom.

Correct Answer: C. The mass number represents the total number of protons and neutrons in the nucleus.

Correct Answer: B. Isobars are atoms with the same mass number but different atomic numbers.

Correct Answer: C. Isotopes of an element differ in the number of neutrons.

Correct Answer: C. Maxwell’s Electromagnetic Theory explains the wave nature of light.

Correct Answer: B. The speed of light in a vacuum is $3.0 \times 10^8$ m/s.

Correct Answer: B. The relationship between frequency, wavelength, and the speed of light is given by the equation c = $\nu\lambda$.

Correct Answer: A. Electromagnetic radiation consists of oscillating electric and magnetic fields.

Correct Answer: D. The visible light portion of the electromagnetic spectrum is visible to the human eye.

Correct Answer: B. Planck’s Quantum Theory proposed that energy is quantized, meaning it comes in discrete amounts.

Correct Answer: A. The smallest unit of electromagnetic energy is called a photon.

Correct Answer: C. The Photoelectric Effect demonstrated the particle nature of light by ejecting electrons from a metal surface.

Correct Answer: B. Albert Einstein explained the photoelectric effect using Planck’s Quantum Theory.

Correct Answer: D. The energy of a photon is related to its frequency and wavelength.

Correct Answer: B. No electrons are emitted below a certain threshold frequency, specific to each metal.

Correct Answer: B. Emission spectra occur when atoms release energy and return to a lower energy state.

Correct Answer: B. The Balmer series corresponds to the visible light region of the hydrogen spectrum.

Correct Answer: B. Helium was first discovered through its spectrum in the Sun.

Correct Answer: D. The Rydberg formula is used to predict the wavelengths of hydrogen spectral lines.

Correct Answer: B. Each element has a unique line spectrum.

Correct Answer: B. A line spectrum indicates that energy levels in an atom are quantized.

Correct Answer: B. The Lyman series of hydrogen spectral lines appears in the ultraviolet region.

Correct Answer: B. The Paschen series appears in the infrared region.

Correct Answer: C. Johann Balmer first observed and studied the line spectrum of hydrogen.

Correct Answer: B. The Rydberg constant is used to predict the wavelengths of hydrogen spectral lines.

Correct Answer: B. According to Bohr’s Model, the electron in a hydrogen atom moves in fixed circular orbits around the nucleus.

Correct Answer: C. Bohr’s model is based on the concept that electrons exist in quantized orbits around the nucleus.

Correct Answer: C. The energy of an electron decreases as it moves closer to the nucleus, not increases.

Correct Answer: C. The energy absorbed or emitted during a transition is equal to the difference between the energies of the two levels.

Correct Answer: C. Bohr’s model assumes that electrons do not radiate energy while in stable orbits, explaining the stability of the atom.

Correct Answer: A. A limitation of Bohr’s Model is that it applies only to atoms with one electron, such as hydrogen.

Correct Answer: B. In Bohr’s model, the energy of the electron in the nth orbit is inversely proportional to n².

Correct Answer: A. The energy of the electron in the first orbit of hydrogen (n = 1) is –$2.18 \times 10^{-18}$ J.

Correct Answer: B. In Bohr’s Model, the ground state refers to the electron being in the first orbit (n = 1).

Correct Answer: B. Bohr’s model can be applied to hydrogen-like ions such as He⁺ and Li²⁺.

Correct Answer: C. For hydrogen-like ions, the energy of the electron in the nth orbit is directly proportional to Z².

Correct Answer: B. The radius of the electron orbit in hydrogen-like ions is inversely proportional to Z.

Correct Answer: A. The energy levels for hydrogen-like ions are given by the expression $E_n = –2.18 \times 10^{-18} Z/n^2$.

Correct Answer: C. Louis de Broglie proposed the wave-particle duality of matter.

Correct Answer: B. The Heisenberg Uncertainty Principle states that the exact position and momentum of a particle cannot be simultaneously determined.

Correct Answer: B. According to the de Broglie hypothesis, the wavelength of a particle is inversely proportional to its mass.

Correct Answer: B. The de Broglie wavelength is significant for subatomic particles, such as electrons.

Correct Answer: B. The principal quantum number defines the size and energy of an orbital.

Correct Answer: C. The azimuthal quantum number determines the shape of an orbital.

Correct Answer: A. For a given principal quantum number (n), the possible values of the azimuthal quantum number (l) range from 0 to n-1.

Correct Answer: B. The magnetic quantum number represents the orientation of the orbital in space.

Correct Answer: B. For an s-orbital, the azimuthal quantum number (l) is 0.

Correct Answer: C. The p-orbitals have 3 possible orientations.

Correct Answer: C. The spin quantum number ($m_s$) has the possible values +½ or –½.

Correct Answer: B. The p-orbital has a dumbbell shape.

Correct Answer: B. The maximum number of electrons that can occupy an orbital is 2.

Correct Answer: C. The Aufbau principle states that electrons are added to orbitals in order of increasing orbital energy.

Correct Answer: B. The Pauli Exclusion Principle states that no two electrons in the same atom can have the same set of quantum numbers.

Correct Answer: C. Hund’s Rule of Maximum Multiplicity states that electrons must occupy orbitals singly before pairing.

Correct Answer: C. According to Hund’s Rule, the electrons will occupy each p orbital singly (↑ ↑ ↑) before pairing.

Correct Answer: B. The Aufbau principle explains that electrons occupy the most stable and lowest energy configuration.

Correct Answer: C. Hund’s Rule ensures that electrons in an atom minimize repulsion by occupying separate orbitals.

Correct Answer: B. The electronic configuration describes the arrangement of electrons in an atom’s orbitals.

Correct Answer: A. The electronic configuration of oxygen is 1s² 2s² 2p⁴.

Correct Answer: A. The electronic configuration of sodium is 1s² 2s² 2p⁶ 3s¹.

Correct Answer: A. Phosphorus has the electronic configuration 1s² 2s² 2p⁶ 3s² 3p³.

Correct Answer: A. The element with atomic number 10 (neon) has the electronic configuration 1s² 2s² 2p⁶.

Correct Answer: B. Nitrogen (N) has a half-filled p-orbital in its ground state (1s² 2s² 2p³).