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Atomic Structure

  1. Jul 11, 2010 #1
    Please help me in clearing my basic doubt

    We all know that positive charges are concentrated at the centre of the atom , known as nucleus and electrons revolves around the nucleus in orbits. Is it necessary to assume that orbits are circular ?
  2. jcsd
  3. Jul 11, 2010 #2
    Be careful. A classical picture of "electrons revolv[ing] around the nucleus in orbits" is not correct in a literal sense. An atom is a quantum mechanical system, and the electrons can only be described by their wavefunction, rather than a well-defined trajectory.

    With that said, one needs to make no assumptions about the shape of these wavefunctions. They can be calculated. Some of them are spherically symmetric (the probability of finding that electron only depends on the distance from the nucleus), but others are not.
  4. Jul 11, 2010 #3


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    Note also, that the quantum mechanical description of the atom is probably something that is accessible at the college level. Until you have reached the necessary level of preparation, there is always the Bohr model, which provides several useful insights and conveys many of the key characteristics of the quantum mechanical description, but is not quite as accurate as it. Within the Bohr model of the atom, the nucleus is considered to be a heavy positively charged point at the center of the atom, and negatively charged point-like electrons revolve around the nucleus in circular orbits.
  5. Jul 11, 2010 #4
    short answer: no. but it has some usefulness as noted.

    Try reading the Wikipedia introductions for "electron orbital" ...both atomic and molecular....
    you might also try reading Wikipedia about 'electrical conductors'...where conuction electrons move along a conductor as in a current carrying copper wire.
  6. Jul 11, 2010 #5
  7. Jul 11, 2010 #6


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    Right. It also happens that the ones which are spherically symmetric (s-orbitals) correspond to cases where the electron has no angular momentum. So if you were to attempt to describe the motion classically (bearing in mind that they don't actually have trajectories) it'd be more correct to say the electrons are moving 'inwards and outwards' from the nucleus, rather than 'orbiting' it.

    This is part of the reason why classical/semiclassical models of the atom ultimately can't work; because there's no way that something moving as a classical particle can have a spherically symmetrical pattern of motion without having any angular momentum. (this is only one of several deficiencies of the Bohr model)
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