Rutherford's Experiment Quiz
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Questions and Answers

What percentage of alpha particles passed straight through the atom in Rutherford's experiment?

  • 75%
  • 99% (correct)
  • 50%
  • 10%

    • All alpha particles were deflected in Rutherford's scattering experiment.

    False (B)

    What is suggested about the space inside an atom based on Rutherford's findings?

    The space inside the atom is hollow or empty.

    One in __________ alpha particles reflected or returned back suffering a deflection of 180 degrees.

    <p>20000</p> Signup and view all the answers

    Match the following observations with their outcomes:

    <p>Most alpha particles passed straight through = Atom is mostly empty Some particles deflected at different angles = Presence of a positively charged nucleus Few particles deflected 90 degrees = Indicates small nucleus size One in 20000 particles reflected = Nucleus possesses considerable mass</p> Signup and view all the answers

    What particles did Rutherford use to bombard the gold sheet in his experiment?

    <p>Alpha particles (D)</p> Signup and view all the answers

    Rutherford's experiment involved a gold sheet that was 0.006 cm thick.

    <p>False (B)</p> Signup and view all the answers

    In what year did Rutherford perform his alpha particle scattering experiment?

    <p>1911</p> Signup and view all the answers

    The flashes produced by alpha particles on a zinc sulphide screen are known as __________.

    <p>scintillations</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Alpha particles = Helium ions used in experiments Zinc sulphide = Material used to observe scintillations Scintillations = Flashes of light produced when particles hit a screen Gold sheet = Thin material used for particle bombardment</p> Signup and view all the answers

    What is the primary feature of Rutherford's nuclear model of the atom?

    <p>An atom consists of a positively charged nucleus with moving electrons. (D)</p> Signup and view all the answers

    Rutherford's model successfully explains the stability of the atom.

    <p>False (B)</p> Signup and view all the answers

    What is the estimated size of the nucleus in Rutherford's model?

    <p>10^{-13} cm</p> Signup and view all the answers

    Almost the entire mass of the atom is concentrated in the __________.

    <p>nucleus</p> Signup and view all the answers

    Match the following characteristics with their definitions:

    <p>Positive nucleus = Center of the atom containing protons Electrons = Negatively charged particles orbiting the nucleus Coulombic force = Attractive force between electrons and protons Spiral motion = Predicted behavior of electrons in classical physics</p> Signup and view all the answers

    Which of the following describes a limitation of Rutherford's atomic model?

    <p>It could not account for the stability of atoms. (C)</p> Signup and view all the answers

    Rutherford proposed that electrons and protons are held together through gravitational attraction.

    <p>False (B)</p> Signup and view all the answers

    What type of atomic spectra did hydrogen produce according to Rutherford's model?

    <p>Discontinuous spectra or line spectra</p> Signup and view all the answers

    What are small packets of energy called in Bohr's atomic model?

    <p>Quanta (C)</p> Signup and view all the answers

    Electrons can exist in any orbit around the nucleus according to Bohr's atomic model.

    <p>False (B)</p> Signup and view all the answers

    What does the equation for the radius of the nth orbit of a hydrogen atom indicate?

    <p>Radius increases with the square of the principal quantum number. (A)</p> Signup and view all the answers

    Bohr's atomic model can explain the splitting of spectral lines under a magnetic field.

    <p>False (B)</p> Signup and view all the answers

    What is the equation for the energy levels of an electron in a hydrogen-like atom?

    <p>E_n = -2.178x10^-18 J/n^2</p> Signup and view all the answers

    An electron jumps from a higher energy level to a lower energy level by _______ energy.

    <p>releasing</p> Signup and view all the answers

    What type of atomic spectrum is produced when an atom absorbs certain wavelengths of light?

    <p>Absorption spectrum</p> Signup and view all the answers

    The series of bright lines produced by a heated atom is called __________.

    <p>emission spectrum</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Quanta = Small packets of energy Stationary states = Specific electron orbits Energy emitted = Electron falls to a lower energy level E_n = Energy level equation for hydrogen-like atoms</p> Signup and view all the answers

    Which of the following correctly describes the angular momentum of an electron in the Bohr model?

    <p>It is quantized. (D)</p> Signup and view all the answers

    Match the atomic spectra with their descriptions:

    <p>Absorption spectrum = Dark lines on a bright background Emission spectrum = Bright lines on a dark background</p> Signup and view all the answers

    Which of the following is a limitation of Bohr's atomic model?

    <p>It does not adequately explain the fine structure of hydrogen's spectral lines. (D)</p> Signup and view all the answers

    Bohr's model successfully explains the atomic spectra of multi-electronic species.

    <p>False (B)</p> Signup and view all the answers

    What role does energy difference play in the atomic spectra observed?

    <p>It corresponds to the energy of absorbed or emitted photons.</p> Signup and view all the answers

    All atoms produce continuous spectra.

    <p>False (B)</p> Signup and view all the answers

    What is the principle quantum number for the first orbit in a hydrogen atom?

    <p>1</p> Signup and view all the answers

    The splitting of spectral lines in the presence of an electric field is known as the __________ effect.

    <p>Stark</p> Signup and view all the answers

    What did Bohr's model fail to account for regarding chemical bonds?

    <p>The formation of chemical bonds to create more stable molecules. (B)</p> Signup and view all the answers

    Which spectral series corresponds to electrons returning to the first energy level?

    <p>Lyman series (A)</p> Signup and view all the answers

    The wavelength of radiation for the Balmer series is in the ultraviolet region.

    <p>False (B)</p> Signup and view all the answers

    What is the range of wavelengths for the Paschen series?

    <p>95,000-18,750 Å</p> Signup and view all the answers

    The first line in the Balmer series is known as __________.

    <p>H_alpha</p> Signup and view all the answers

    Which equation is used to calculate the wavelength of emission?

    <p>$ar{ u} = R_H \left(\frac{1}{n_1^2} - \frac{1}{n_2^2} \right)$ (D)</p> Signup and view all the answers

    Match the spectral series with their corresponding lower energy levels (n1):

    <p>Lyman series = 1 Balmer series = 2 Paschen series = 3 Bracket series = 4 Pfund series = 5 Humphreys series = 6</p> Signup and view all the answers

    The Pfund series corresponds to transitions of electrons to the fifth energy level.

    <p>True (A)</p> Signup and view all the answers

    What constant is represented by R in the Balmer equation?

    <p>Rydberg's constant</p> Signup and view all the answers

    Which series of emission line spectra does the hydrogen atom produce?

    <p>Five series (C)</p> Signup and view all the answers

    The atomic spectrum of hydrogen is a continuous spectrum.

    <p>False (B)</p> Signup and view all the answers

    What is the energy formula for the transition between two energy levels in an atom?

    <p>ΔE = E₂ - E₁ = hv</p> Signup and view all the answers

    The series of colored bands produced when sunlight is split is known as the __________ spectrum.

    <p>continuous</p> Signup and view all the answers

    Match the following types of spectra with their characteristics:

    <p>Continuous Spectrum = Made of colors with no gaps Discontinuous Spectrum = Composed of lines or bands Atomic Spectrum = Discrete lines representing fixed wavelengths Molecular Spectrum = Bands separated by dark spaces</p> Signup and view all the answers

    What is the result of an electron in a hydrogen atom moving to a lower energy level?

    <p>It emits energy (A)</p> Signup and view all the answers

    Hydrogen emits the same wavelengths in both absorption and emission spectra.

    <p>True (A)</p> Signup and view all the answers

    What happens to an electron when it absorbs energy in an atom?

    <p>It gets promoted to a higher energy level.</p> Signup and view all the answers

    What was one conclusion made by Rutherford from his experiments?

    <p>The nucleus contains most of the atom's mass. (B)</p> Signup and view all the answers

    Rutherford selected gold foil because it is a good conductor of heat.

    <p>False (B)</p> Signup and view all the answers

    Who proposed the model of the atom that addressed the limitations of Rutherford's model?

    <p>Niels Bohr</p> Signup and view all the answers

    Which principle explains the uncertainty in the position and velocity of an electron?

    <p>Heisenberg's Uncertainty Principle (D)</p> Signup and view all the answers

    Bohr's model of the atom fully explains the wave nature of electrons.

    <p>False (B)</p> Signup and view all the answers

    In Bohr's atomic model, electrons occupy certain definite circular paths called ______.

    <p>orbits</p> Signup and view all the answers

    What is the significance of de Broglie's concept in the quantum mechanical model?

    <p>It introduced the wave nature of electrons.</p> Signup and view all the answers

    According to Bohr's model, what is the relationship between energy levels and the distance from the nucleus?

    <p>Energy levels increase as distance from the nucleus increases. (B)</p> Signup and view all the answers

    The electron's energy at infinite distance is assumed to be __________.

    <p>zero</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Ground state = An electron's lowest energy state Excited state = An electron's higher energy state Photon = Quantum of electromagnetic radiation Orbitals = Regions where electrons are likely to be found</p> Signup and view all the answers

    Match the energy levels of electron orbits to their corresponding values:

    <p>n = 1 = -0.38 eV n = 2 = -0.85 eV n = 3 = -1.15 eV n = 4 = -3.4 eV</p> Signup and view all the answers

    In Bohr's model, electrons can emit or absorb energy only while changing orbits.

    <p>True (A)</p> Signup and view all the answers

    Which of the following best describes the quantum mechanical model of the atom?

    <p>Atoms are positively charged nuclei with electron clouds surrounding them. (A)</p> Signup and view all the answers

    What is the formula that relates the energy difference between two orbits?

    <p>ΔE = E₂ - E₁ = hv</p> Signup and view all the answers

    Why does the energy of an electron become negative as it moves closer to the nucleus?

    <p>The electron does work against the electrostatic attraction, thus lowering its energy.</p> Signup and view all the answers

    Electrons can jump into the nucleus of an atom under standard conditions.

    <p>False (B)</p> Signup and view all the answers

    What term did Louis de Broglie use to describe the wave nature of particles?

    <p>Matter waves (B)</p> Signup and view all the answers

    The wave character of an electron was verified by the photoelectric effect.

    <p>False (B)</p> Signup and view all the answers

    What is the equation derived by de Broglie for the wavelength of a particle?

    <p>λ = h / p</p> Signup and view all the answers

    The energy of a photon is calculated using ________ equation.

    <p>Planck's</p> Signup and view all the answers

    Match the following concepts with their descriptions:

    <p>Wave nature = Resembles light in behavior Particle nature = Describes localized matter de Broglie's wavelength = Inversely proportional to mass Electron diffraction = Verifies wave character of electrons</p> Signup and view all the answers

    Which of the following best explains why de Broglie's concept is significant for microscopic particles?

    <p>Their wavelengths are negligible for large objects. (C)</p> Signup and view all the answers

    The de Broglie equation applies to both microscopic and macroscopic particles.

    <p>False (B)</p> Signup and view all the answers

    What experimental setup verified the wave nature of electrons?

    <p>Electron diffraction experiment</p> Signup and view all the answers

    Study Notes

    Rutherford's Atomic Model

    • Ernest Rutherford, a student of J.J. Thompson, proposed an atomic model in 1911 after conducting an alpha particle scattering experiment.
    • The experiment involved bombarding a thin sheet of gold (0.00006 cm thick) with α-particles equivalent to helium ions (He²⁺), sourced from a radioactive substance.
    • Scattering of α-particles was observed on a circular zinc sulfide fluorescent screen, leading to the detection of tiny flashes (scintillations) with a microscope.

    Rutherford α-Particle Scattering Experiment

    • Various outcomes were observed for the bombarded α-particles:
      • Straight-passed particles
      • Slightly deflected particles
      • Heavily deflected particles
      • Reflected particles

    Observations from the Experiment

    • About 99% of α-particles passed straight through the gold foil.
    • Some α-particles were deflected at small angles.
    • Roughly 1 in 10,000 α-particles was deflected at angles up to 90 degrees or more.
    • 1 in 20,000 α-particles reflected back, indicating deflections of 180 degrees.

    Conclusions from Experiment

    • Atoms largely consist of empty space since most α-particles passed straight through.
    • A significant positively charged nucleus must exist, as deflections suggest interaction with positively charged particles.
    • The nucleus occupies a tiny volume (radius of 10⁻¹³ cm) compared to the entire atom (radius around 10⁻⁸ cm).
    • The nucleus contains most of the atom’s mass, reflecting the relatively heavy α-particles.

    Rutherford's Nuclear Model

    • Proposed in 1911, highlighting:
      • A positively charged nucleus surrounded by moving electrons.
      • Electrons occupy a large electronic cloud, approximately 10⁵ times the nucleus size.
      • Equal numbers of electrons and protons ensure electrical neutrality.
      • The nucleus contains almost the entire atomic mass.
      • Electrons move around the nucleus due to electrostatic attraction balanced by their centrifugal motion.

    Limitations of Rutherford's Atomic Model

    • The model failed to explain atomic stability, as moving electrons would radiate energy and spiral into the nucleus.
    • It could not account for the discrete line spectra observed in atoms, as a continuous energy loss would lead to continuous spectra.

    Bohr's Model of the Atom

    • Niels Bohr introduced improvements in 1913, addressing shortcomings in Rutherford's model.
    • He applied quantum theory to explain atomic stability and spectra, earning a Nobel Prize in Physics (1922).

    Postulates of Bohr's Atomic Model

    • Electrons exist in specific, quantized orbits around the nucleus.
    • Each orbit has associated energy levels (K, L, M, N, etc.).
    • Electrons remain in fixed orbits without energy loss until they absorb or emit energy, causing transitions between energy levels.
    • Energy levels are quantized, defined mathematically; higher orbits have higher energy.
    • The angular momentum of electrons in orbits is quantized (integer multiples of h/2π).

    Applications of Bohr's Model

    • Successfully explained atomic stability and spectra of hydrogen and hydrogen-like atoms.
    • Derived energy and radius relationships for these systems.

    Defects of Bohr's Theory

    • Cannot explain the splitting of spectral lines (fine structure).
    • Doesn't account for multi-electron species spectra.
    • Lacks justification for angular momentum quantization.
    • Assumes electrons move in fixed circular paths (ignoring three-dimensional movement).
    • Does not explain Zeeman and Stark effects or chemical bond formation.

    Atomic Spectra

    • Absorption and emission spectra arise from electron energy transitions.
    • Series of dark and bright lines correspond to specific wavelengths in atomic spectra.
      • Absorption spectra: dark lines appear against a white light background due to characteristic wavelengths absorbed.
      • Emission spectra: bright lines on dark backgrounds when atoms emit energy while returning to ground states.

    Spectrum of Hydrogen Atom

    • Hydrogen exhibits five series of emission lines:
      • Lyman series (UV region)
      • Balmer series (visible region)
      • Paschen, Bracket, Pfund series (infrared regions)
    • Spectral series arise from electronic transitions between energy levels, quantified by Rydberg's formula.

    Quantum Mechanical Model of the Atom

    • Developed by Erwin Schrödinger, integrating wave-particle duality and the uncertainty principle.
    • Electrons are described as waves rather than fixed bodies in defined paths, extending the model's application.

    Concept of Negative Electronic Energy

    • Energy at an infinite distance is set to zero, with negative energies indicating attraction to the nucleus as electrons move closer.

    Self-Practice Questions

    • Why does hydrogen display numerous line spectra despite having one electron?
    • What prevents electrons from falling into the nucleus?
    • Define quantization of angular momentum for electrons in orbits.
    • Why are energy levels negative in this model?### Origin of Line Spectra of Hydrogen
    • Hydrogen energy levels exhibit quantized states with specific energies:
      • Ground state (n=1) at -0.38 eV
      • Second level (n=2) at -0.85 eV
      • Third level (n=3) at -1.15 eV
      • Fourth level (n=4) at -3.4 eV
      • Fifth level (n=5) at -13.4 eV
    • Various series of spectral lines correspond to transitions between these energy levels:
      • Lyman series (UV region)
      • Balmer series (visible region)
      • Paschen, Brackett, Pfund, and Humphreys series (infrared region)

    The de Broglie Concept (Wave-Particle Duality)

    • Louis de Broglie introduced the concept of wave-particle duality in 1924, stating that electrons exhibit both particle and wave characteristics.
    • Matter waves are distinct from mechanical waves (e.g., sound) and electromagnetic waves (e.g., light).
    • The particle nature of electrons is illustrated by the photoelectric effect; while the wave nature is demonstrated through electron diffraction experiments.
    • Electron microscopes utilize the wave-like behavior of electrons similar to light waves.

    Derivation of de Broglie's Wave Equation

    • Einstein's mass-energy equivalence: (E = mc^2)
    • Planck's equation for photon energy: (E = hv)
    • By manipulating these equations, the relationship between mass and wavelength for moving particles can be derived:
      • (λ = \frac{h}{mv}) where (p = mv) (momentum)
    • This equation provides the wavelength of an electron, referred to as de Broglie's wavelength, which is very small and significant primarily for submicroscopic particles.

    Significance of de Broglie Equation

    • Establishes a relationship between the wave and particle nature of matter: The wavelength of moving particles is inversely related to their mass.
    • Applicable to all matter, but especially critical for subatomic particles due to negligible wavelengths for larger objects.
    • Supports the quantization of angular momentum in atomic structures, aligning with Bohr's model of the atom.

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    Test your knowledge on Rutherford's gold foil experiment! This quiz covers key findings, including the behavior of alpha particles and what they reveal about atomic structure. Understand the significance of the deflections and reflections of alpha particles in uncovering the atom's composition.

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