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Questions and Answers
What did Thomson propose in his atom model?
What did Thomson propose in his atom model?
Thomson proposed that atom can be regarded as a sphere of positive charge with negatively charged electrons uniformly distributed.
What are the key features of Rutherford's atom model?
What are the key features of Rutherford's atom model?
Rutherford's atom model consists of a positively charged nucleus with electrons revolving around it, held together by electrostatic force of attraction.
What is the main drawback of Rutherford's atom model?
What is the main drawback of Rutherford's atom model?
It cannot explain the stability of an atom and fails to explain the spectrum of hydrogen.
What were the observations from Rutherford's gold foil experiment?
What were the observations from Rutherford's gold foil experiment?
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Define the photoelectric effect.
Define the photoelectric effect.
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What are the key postulates of Bohr's atom model?
What are the key postulates of Bohr's atom model?
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What are the merits of Bohr's atom model?
What are the merits of Bohr's atom model?
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What criterion determines the permitted orbits in Bohr's model?
What criterion determines the permitted orbits in Bohr's model?
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What did Rutherford's gold foil experiment reveal about the atom's structure?
What did Rutherford's gold foil experiment reveal about the atom's structure?
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How does the electron behave in Bohr's atom model?
How does the electron behave in Bohr's atom model?
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What did Rutherford's gold foil experiment reveal about the atom's structure?
What did Rutherford's gold foil experiment reveal about the atom's structure?
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Define the photoelectric effect.
Define the photoelectric effect.
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What is the main drawback of Rutherford's atom model?
What is the main drawback of Rutherford's atom model?
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What are the key postulates of Bohr's atom model?
What are the key postulates of Bohr's atom model?
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Explain the spectral lines in the spectrum of hydrogen.
Explain the spectral lines in the spectrum of hydrogen.
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What does Thomson's atom model propose?
What does Thomson's atom model propose?
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What are the merits of Bohr's atom model?
What are the merits of Bohr's atom model?
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Explain the concept of the ejection of electrons when light falls on a metal.
Explain the concept of the ejection of electrons when light falls on a metal.
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What are the observations from Rutherford's gold foil experiment?
What are the observations from Rutherford's gold foil experiment?
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Explain the key features of Thomson's atom model.
Explain the key features of Thomson's atom model.
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Study Notes
Thomson's Atom Model
- Proposed the "plum pudding" model, where electrons are embedded in a positively charged sphere.
- Suggested that atoms are uniform and not composed of smaller particles.
- Demonstrated the presence of electrons, challenging the idea of indivisible atoms.
Rutherford's Atom Model
- Key features include a dense central nucleus with positively charged protons, surrounded by orbiting electrons.
- Introduced the idea of empty space within an atom, with electrons occupying specific orbits around the nucleus.
- Moved away from Thomson's model, emphasizing a core nucleus responsible for most of an atom's mass.
Main Drawback of Rutherford's Atom Model
- Failed to explain the stability of electron orbits; electrons would spiral into the nucleus due to electromagnetic attraction.
- Did not account for atomic spectra or the quantization of energy levels.
Observations from Rutherford's Gold Foil Experiment
- Most alpha particles passed through the foil, indicating mostly empty space in atoms.
- A small fraction were deflected at large angles, suggesting a concentrated positive charge within the nucleus.
- Enabled the conclusion that atoms consist of a dense nucleus surrounded by electrons.
Photoelectric Effect
- Phenomenon where electrons are ejected from a material (usually metals) when exposed to light of sufficient energy.
- Demonstrated the particle-like properties of light, essential for establishing quantum theory.
Key Postulates of Bohr's Atom Model
- Electrons travel in fixed, quantized orbits around the nucleus without radiating energy.
- Each orbit corresponds to a specific energy level; transitions between levels result in the absorption or emission of light.
- Angular momentum of electrons in orbits is quantized and is an integral multiple of (h/2\pi).
Merits of Bohr's Atom Model
- Accurately explained the spectral lines of hydrogen and predicted their wavelengths.
- Introduced the concept of quantized energy levels, resolving issues with Rutherford's model.
- Provided a foundation for future quantum mechanics theories.
Permitted Orbits in Bohr's Model
- Determined by the quantization of angular momentum ((mvr = n(h/2\pi))), where (m) is electron mass, (v) is velocity, (r) is orbit radius, (n) is a positive integer, and (h) is Planck's constant.
- Only certain orbits are allowed; electrons can only exist in these specific states.
Electron Behavior in Bohr's Atom Model
- Electrons occupy fixed energy levels and can move between these levels by absorbing or emitting a quantum of energy.
- In stable orbits, they do not lose energy but can jump to higher levels when sufficient energy is provided.
Explanation of Spectral Lines in Hydrogen's Spectrum
- Caused by electron transitions between energy levels, emitting or absorbing light at specific wavelengths.
- Each transition corresponds to a unique spectral line, observed in hydrogen's emission and absorption spectra.
Concept of Ejection of Electrons
- Light striking a metal surface transfers energy to electrons; when the energy exceeds a threshold, electrons are expelled.
- This principle is foundational for applications such as photoelectric sensors and solar panels.
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Description
Test your knowledge on the Thomson and Rutherford atom models with this quiz. Explore the key concepts of each model and understand their drawbacks. Challenge yourself with questions on atomic structure and historical developments in atomic theory.
