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What are postulates of Bohr's model of hydrogen atom? Write its limitations.
What are postulates of Bohr's model of hydrogen atom? Write its limitations.
- Electrons in an atom revolve around nucleus in certain fixed circular paths called orbits. Each orbit has fixed amount of energy. So these orbits are also called energy levels. These orbits are numbered as 1,2,3,4.... (or) K, L, M, N......
- As long as an electron revolves around the nucleus in a fixed orbit it does not emit (or) absorb energy. So these orbits are also called as Stationary orbits.
- Angular momentum of revolving electron is an integral multiple of h/2π .... mvr = nh/2π Here, m= mass of electron, v= velocity, r= radius and h= Plancks' constant
- Energy is emitted (or) absorbed when electron jumps from one orbit to another orbit. The energy difference between two orbits is ΔE = E2-E1 = hv Here, E2= Energy of the higher orbit, E1= Energy of the lower orbit
Limitations of Bohr's model:
- Bohr's theory fails to explain the fine spectrum of Hydrogen.
- It fails to explain the spectra of multi electron atoms like He, Li, Be etc.,
- It could not explain the Zeeman effect.
- It could not explain the Stark effect.
- It is against to de-Broglie's wave nature and Heisenberg's uncertainty principle.
- It fails to explain doublets of hydrogen atom spectrum.
Give any two differences between emission and absorption spectra.
Give any two differences between emission and absorption spectra.
Differences between Emission Spectrum and Absorption Spectrum: Emission spectrum
- It is produced due to emission of energy by an excited substance.
- It is produced when electrons jump from higher orbits to lower orbits.
- It has bright lines on dark back ground.
Absorption Spectrum:
- It is produced due to absorption of energy by a substance.
- It is produced when electrons jump from lower orbits to higher orbits.
- It has dark lines on bright back ground.
Study Notes
Bohr's Model of the Hydrogen Atom
- Electrons orbit the nucleus in fixed circular paths called orbits
- Each orbit has a fixed amount of energy, labeled as 1, 2, 3... (or K, L, M, N...)
- As long as an electron stays in a fixed orbit, it doesn't emit or absorb energy, these paths are also called stationary orbits.
- Angular momentum of the revolving electron is an integral multiple of h/2π (mvr = nh/2π)
- Energy is emitted or absorbed when an electron jumps between orbits. The energy difference (ΔE) between two orbits (E₂ - E₁) is equal to a photon's energy (hv), where E₂ is the higher orbit's energy, and E₁ is the lower.
Limitations of Bohr's Model
- Fails to explain the fine spectrum of hydrogen
- Fails to explain the spectra of multi-electron atoms (like He, Li, Be)
- Can't explain the Zeeman effect
- Can't explain the Stark effect
- Contradicts de Broglie's wave nature and Heisenberg's uncertainty principle
- Fails to explain the doublets in the hydrogen atom spectrum
Emission vs. Absorption Spectra
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Emission Spectrum: Produced by an excited substance emitting energy. Electrons jump from higher to lower orbits resulting in bright lines against a dark background.
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Absorption Spectrum: Produced by a substance absorbing energy. Electrons jump from lower to higher orbits, resulting in dark lines against a bright background.
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Description
Explore the fundamentals of Bohr's model and its significance in understanding atomic structure. This quiz covers the basic concepts of electron orbits, energy levels, and the model's limitations in modern physics. Test your knowledge on how the model contributes to our understanding of atomic behavior.
