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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

Thomson’s atomic model

Every atom is uniformly positive charged sphere of radius of the order of 10-10 m, in which entire mass is uniformly distributed and negative charged electrons are embedded randomly.

The atom as a whole is neutral.

Image result for thomson's atomic model black and white

Limitations of Thomson’s atomic model

1. It could not explain the origin of spectral series of hydrogen and other atoms.

2. It could not explain scattering of α–particles in the Rutherford’s experiment.

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