Atomic models Knowledge-Based Practice

Questions

1. 1.

   In the quantum mechanical model of the atom, which quantum number specifies the spatial orientation of an orbital in three-dimensional space?

   • A) Principal quantum number ($n$)
   • B) Azimuthal quantum number ($l$)
   • C) Spin quantum number ($m_s$)
   • D) Magnetic quantum number ($m_l$)
2. 2.

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

   • A) Atoms are transmuted into different chemical elements as bonds form.
   • B) Atoms dissolve into a continuous fluid of matter and re-solidify into products.
   • C) Atoms are created or destroyed depending on whether the reaction absorbs or releases energy.
   • D) Atoms are combined, separated, or rearranged without being created, destroyed, or transformed into other elements.
3. 3.

   In the study of atomic spectra explained by Bohr's atomic model, which spectral series of the hydrogen atom corresponds to electron transitions from higher energy levels to the $n = 2$ level, producing lines in the visible spectrum?

   • A) Lyman series
   • B) Paschen series
   • C) Brackett series
   • D) Balmer series
4. 4.

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

   • A) All atoms of a given element possess identical mass and properties.
   • B) Atoms of different chemical elements combine in fixed, whole-number ratios to form compounds.
   • C) Atoms cannot be subdivided into smaller subatomic particles.
   • D) Chemical reactions involve only the combination, separation, or rearrangement of atoms.
5. 5.

   By applying mutually perpendicular electric and magnetic fields to cathode rays, which physical property of the electron was J. J. Thomson able to determine experimentally?

   • A) The charge-to-mass ratio
   • B) The magnitude of the elementary charge
   • C) The absolute rest mass
   • D) The intrinsic spin angular momentum
6. 6.

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

   • A) It is directly proportional to $n^2$.
   • B) It is directly proportional to $n$.
   • C) It is inversely proportional to $n$.
   • D) It is inversely proportional to $n^2$.
7. 7.

   In Rutherford's alpha-particle scattering experiment, which interaction is primarily responsible for deflecting alpha particles at large angles as they pass through the gold foil?

   • A) Strong nuclear attraction between the alpha particle and the gold nucleus
   • B) Gravitational attraction between the alpha particle and the gold nucleus
   • C) Electrostatic repulsion between the positive alpha particle and the positive gold nucleus
   • D) Magnetic force exerted on the alpha particle by the orbiting atomic electrons
8. 8.

   Which unexplained discrepancy in Rutherford's nuclear atomic model was resolved by James Chadwick's discovery of the neutron in 1932?

   • A) The discrepancy between an atom's positive nuclear charge and its total atomic mass
   • B) The continuous electromagnetic radiation predicted for orbiting electrons by classical physics
   • C) The appearance of discrete emission lines in the atomic spectrum of excited hydrogen
   • D) The wave-particle duality and spatial indeterminacy of atomic electrons
9. 9.

   In the wave explanation of Bohr's atomic model, which condition ensures that an electron forms a stable standing wave in an allowed circular orbit?

   • A) The electron's orbital speed must equal an integer fraction of the speed of light.
   • B) The radius of the orbit must be an odd-integer multiple of the Planck length.
   • C) The circumference of the orbit must equal an integer number of de Broglie wavelengths.
   • D) The orbital frequency must match the frequency of the radiation absorbed during excitation.
10. 10.

    Which experimental finding provided the first direct evidence that atoms contain internal subatomic constituents, disproving Dalton's postulate of indivisible atoms?

    • A) The large-angle deflection of alpha particles passing through thin gold foil
    • B) The deflection of cathode rays by electric and magnetic fields toward a positive plate
    • C) The discrete emission spectra produced by energized hydrogen gas in discharge tubes
    • D) The suspension of charged oil droplets between two oppositely charged horizontal plates
11. 11.

    Which empirical observation directly motivated Niels Bohr to incorporate quantized energy levels into his atomic model?

    • A) The continuous thermal spectrum emitted by heated blackbody radiators
    • B) The discrete line emission spectra produced by hydrogen gas
    • C) The large-angle scattering of alpha particles by thin gold foils
    • D) The deflection of cathode rays by external electric and magnetic fields
12. 12.

    According to Niels Bohr's atomic model, which physical property of an electron is quantized in integer multiples of $\frac{h}{2\pi}$?

    • A) Linear momentum
    • B) Orbital angular momentum
    • C) Kinetic energy
    • D) Electrostatic force
13. 13.

    Which major limitation of Niels Bohr's atomic model demonstrated the need for the modern quantum mechanical model of the atom?

    • A) It contradicted the existence of a dense, positively charged atomic nucleus.
    • B) It predicted that orbiting electrons would continuously radiate energy and spiral into the nucleus.
    • C) It failed to explain why chemical reactions obey the law of conservation of mass.
    • D) It was unable to accurately account for the emission spectra of multi-electron atoms.
14. 14.

    In Rutherford's alpha-particle scattering experiment, which observation provided direct evidence that an atom consists primarily of empty space?

    • A) The vast majority of alpha particles passed straight through the foil with little or no deflection.
    • B) A tiny fraction of alpha particles bounced straight back toward the radiation source.
    • C) Alpha particles were uniformly absorbed as they penetrated the gold foil.
    • D) Negatively charged electrons were continuously ejected from the gold foil surface.
15. 15.

    According to classical electrodynamics, which major theoretical contradiction caused Rutherford's planetary atomic model to be considered unstable?

    • A) It failed to explain why electrons and protons carry equal magnitudes of electric charge.
    • B) It predicted that atoms would emit discrete line spectra rather than a continuous spectrum.
    • C) It could not mathematically account for the mass contributed by uncharged nuclear particles.
    • D) It predicted that orbiting electrons would continuously radiate energy and spiral into the nucleus.
16. 16.

    Which atomic model abandons fixed circular paths for electrons and instead describes electron locations using probability distributions known as orbitals?

    • A) Bohr model
    • B) Quantum mechanical model
    • C) Thomson model
    • D) Rutherford model
17. 17.

    Which atomic model proposed that elements consist of indivisible, indestructible solid spheres with no internal subatomic structure?

    • A) Bohr model
    • B) Rutherford model
    • C) Thomson model
    • D) Dalton model
18. 18.

    Which atomic model proposed that an atom is composed of a uniform sphere of positive charge with negatively charged electrons embedded throughout it?

    • A) Dalton's billiard ball model
    • B) Rutherford's nuclear model
    • C) Thomson's plum pudding model
    • D) Bohr's planetary model
19. 19.

    According to which atomic model do electrons occupy specific, discrete circular orbits with quantized energy, emitting or absorbing radiation only when transitioning between these levels?

    • A) Bohr model
    • B) Thomson model
    • C) Dalton model
    • D) Rutherford model
20. 20.

    Which atomic model first introduced the concept that an atom's positive charge and most of its mass are concentrated in a tiny, dense central nucleus?

    • A) Rutherford's model
    • B) Thomson's model
    • C) Dalton's model
    • D) Bohr's model

Answers and step-by-step solutions appear after you finish the test.