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Why aren't atoms magnets? dont their electrons generate magnetic fields?

  1. Apr 3, 2005 #1
    help pls! since electrons cr8 a magnetic field due to their spin, shouldnt atoms be magnetic? o0
     
  2. jcsd
  3. Apr 3, 2005 #2
    well lets look at the hydrogn atom ( the most abundant and simple atom in the universe) The nucleus of a simple hydrogen atom contains a single charged particle called a Proton and moving around the proton is a single electron. The mass of the electron is close to 2000 times smaller the mass of the proton, the electron carries an amount of charge exactly equal to that of a proton but opposite in sign since opposite charges attract eachother its ELECTROMAGNETIC force which holds the proton and the electron together just as gravity holds our planets to the sun..
     
  4. Apr 3, 2005 #3

    mrjeffy321

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    but both electrons and protons each have a fundamental charge, equal and opposite eachother, so those cancel out eachother.
    but a moving charged particle, like an electron, also creates its own magnetic field, in addition to the fundamental charge it carries.
    how do this work in, since this extra charge doesnt seem to "Cancel" anywhere?
     
  5. Apr 3, 2005 #4
    oh atoms are magnetic:
    Electrons have both orbital mechanical moment and spin.

    moving charge creates magnetic field.

    Electron's magnetic orbital moment due the orbital mechanical moment equals the latter multiplied by the constant named Bohr's Magneton.

    Electron's magnetic moment due spin equals the spin multiplied by twice the Bohr's Magneton.

    (Due to this difference the total magnetic moment of the electron is not collinear with the total mechanical moment)

    Now the nuclei consist of protons and neutrons, which also have their own spin, orbital moments etc, which generally result in certain magnetic moment, not collinear to the total mechanical moment.

    Summarising, it is clear that the total magnetic moment of the whole atom is nonzero, but in some cases (for example zero-level hydrogen atom) it can equal 0...
    did that answer your question?
     
    Last edited by a moderator: Apr 3, 2005
  6. Apr 3, 2005 #5
    Atoms do have magnetic fields (and the spin and precession of the electron creates magnetic fields).

    However these magnetic fields are tought to cancel each other in non-magnetic materials (or the magnetic field is extermely small). In some permanent magnets these spins are aligned in such way that they produce a net magnetic effect.
     
  7. Apr 4, 2005 #6
    o0 heh hemmul sry havent gotten to your level of understanding yet but i think i kind of get it
     
  8. Apr 4, 2005 #7
    opposite charges cannot cancel each other. if the cansel than the force of attraction might fall. if they canscel each other and still be attached then one should have more charge than the other.
    therefore no cancelling is taking place only interaction.
    even resudal forces prove that charges dont cancel each other.

    -Benzun
    newbie
     
  9. Apr 4, 2005 #8

    ZapperZ

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    Not ALL atoms have magnetic moment, at least, not in any measurable sense. Only atoms with (i) valence shell with a non-zero angular momentum (i.e. not an s-orbital), and (ii) one or more unpaired valence shell, are the ones exhibiting clear magnetic moment AND, the predominant source of magnetism in matter. Iron and cromium, for example, have unpaired d-orbitals. This satisfies BOTH criteria above.

    While both the nucleus and the electrons in an atom have their own "spin" angular momentum, these are often too small to detect in the usual magnetic measurements. The nuclear spin is only used in NMR/MRI scenario, but even then not all nucleus exhibit such spins (He4, for example, does not, and below some temperature, condenses into a boson with net spin of 0).

    Zz.
     
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