Collect the information about the scientists who developed the atomic theories

  1. In an attempt to account for the structure of line spectra, Sommerfeld modified Bohr’s atomic model by adding elliptical orbits.
  2. While retaining the first of Bohr’s circular orbit as such, he added one elliptical orbit to Bohr’s second orbit, two elliptical orbits to Bohr’s third orbit etc.
  3. Nucleus of the atom is one of the principal foci of these elliptical orbits because periodic motion under the influence of a central force will lead to elliptical orbits with the force situated at one of the foci.
    Merit: Bohr - Sommerfeld model successful in accounting for the fine line structure of hydrogen atomic spectra.
    Limitations :
  4. This model failed to account for the atomic spectra of atoms of more than one electron.
  5. It did not explain Zeeman and stark effects.
    Bohr’s Model of an Atom :
    Niels Bohr proposed that electrons in an atom occupy ‘stationary’ orbits (states) of fixed energy at different distances from the nucleus.
    When an electron ’jumps’ from a lower energy state (ground state) to higher energy states (excited state) it absorbs energy or emits energy when such a jump occurs from a higher energy state to a lower energy state.
    The energies of an electron in an atom can have only certain values E _{ 1 }, E _{ 2 },
    E _{ 3 }…; that is, the energy is quantized. The states corresponding to these energies
    are called stationary states and the possible values of the energy are called energy levels.