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CBSE NOTES CLASS 12 PHYSICS

CHAPTER 12 ATOMS

Dalton’s atomic theory

Thomson’s atomic model

Limitations of Thomson’s atomic model

Rutherford’s atomic model

Scattering of alpha particles

Electrostatic force between the nucleus and α–particle

Distance of closest approach

Impact parameter

Rutherford’s scattering formula

Limitations of Rutherford atomic model

Bohr’s atomic model

Radius of orbit of electron

Velocity of electron in an orbit

Frequency of electron

Time period of revolution of an electron

Kinetic energy of an electron revolving in an orbit

Potential energy of an electron in an orbit

Total energy of an electron in an orbit

Wave number of an electron in an orbit

Quantum numbers

Hydrogen spectrum series

Lyman series

Balmer series

Paschen series

Brackett series

Pfund series

Line spectra and electron transitions between energy levels

de Broglie’s explanation of Bohr’s second postulate of quantisation

Limitations of Bohr’s atomic model

CBSE NOTES CLASS 12 PHYSICS

CHAPTER 12 ATOMS

Limitations of Bohr’s atomic model

  1. The Bohr model is applicable to hydrogenic atoms. It cannot be extended atoms with more than one electron.

  2. While the Bohr’s model correctly predicts the frequencies of the light emitted by hydrogenic atoms, the model is unable to explain the relative intensities of the frequencies in the spectrum.

  3. Bohr’s model is also unable to explain splitting of spectral lines.
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