• Question: Why are elements iron, cobalt and nickel magnetic yet all elements have electron's orbiting around the nucleus and yet not all elements are magnetic?

    Asked by webbo to Meeks, Pete, Stephen, Steve, Tom on 21 Jun 2010 in Categories: .
    • Photo: Steve Roser

      Steve Roser answered on 14 Jun 2010:

      Its all about pairing up. Most elements gradually build up their electrons in shells which involve pairs – so in the periodic table you get H/He then Na/Mg then a group with three more pairs of electrons. You can think of these as north and south poles, cancelling each other out. In the transition metals, you add electrons one by one til you get 10. Iron then has 4 unpaired up electrons, which all point one way – this gives it a magnetic effect called ferroelectricity. Most elements don’t have these large free, unpaired electrons

    • Photo: Tom Hartley

      Tom Hartley answered on 14 Jun 2010:

      I found the answer on wikipedia, but I am not sure I understand it.

      It’s due to a quantum mechanical effect called Exchange Interaction – nearby atoms with certain electron configurations (the elements you mention) overlap with one another which leads their electrons to align with one another so that their spins do not cancel out as is more usually the case.

      I think I better stop there before I make any serious mistakes (if I haven’t already). I will look in some of my books when I get home and see if I can come up with a better explanation.

    • Photo: Stephen Curry

      Stephen Curry answered on 14 Jun 2010:

      Hello Webbo – That’s another tough one for me. I could be making this up but inside atoms, the orbitals that electrons can occupy are arranged at different energy levels. In each orbital (simplifying a bit) there is room for two electrons. If all the orbitals are paired, the atom is not magnetic. But if you have an orbital with a unpaired electrons (e.g. iron), the atom may be ‘ferromagnetic’.

      However, I may be on thin ice here – it’s been a long time since I was immersed in physics.

      Your question and one on how magnets work have really made me think about this (so thanks!). I’m going to try to find out some more.

    • Photo: Marieke Navin

      Marieke Navin answered on 21 Jun 2010:

      This is a really interesting question and you have to think about the periodic table to answer it. Do you know the periodic table at all, have you done it in school? If you have a look at one (you can find them on google). As you add more electrons to an atom the element changes…it is the configuration of the electrons that give the element its properties…the magnetic materials are all in a similar place on the periodic table – have a look and see

    • Photo: Pete Edwards

      Pete Edwards answered on 21 Jun 2010:

      It’s down to the spin thing – see Steve’s answer 🙂

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