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    Hi!

    I've progressed further onto the stretch and challenge section of this sheet and I'm not sure whether I'm doing this question right or what the second point would be.

    The question says :
    The bonding in aluminium chloride is sometimes described as ionic with some covalent character but magnesium chloride doesn't have this covalent character. Suggest 2 differences between aluminium and magnesium ions that might explain the different types of bonding observed.

    I've put that magnesium ions have a charge of +2 whereas aluminium ions have a charge of +3

    Is this relevant? What else would I need to put for the second suggestion?

    Thanks,
    Blake
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    I believe your point on charges is correct (maybe explain what this means to the lattice), for the second have a look at the electronegativity of aluminium&magnesium when compared to chlorine, and how this links to the different types of bonding, also remember that bonds are often not perfectly ionic/covalent and there is a shift to stronger ionic/covalent bonds across the periodic table.
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    (Original post by JN17)
    I believe your point on charges is correct (maybe explain what this means to the lattice), for the second have a look at the electronegativity of aluminium&magnesium when compared to chlorine, and how this links to the different types of bonding, also remember that bonds are often not perfectly ionic/covalent and there is a shift to stronger ionic/covalent bonds across the periodic table.
    Hi, thanks for the reply, sorry if I'm being stupid but I don't really understand what to do with the electronegativity values now that I've got them. I got 3.16 for chlorine, 1.31 for magnesium and 1.61 for aluminium. I understand that aluminium and magnesium are both much less electronegative than chlorine but I don't really know how this works.
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    (Original post by Blake Jones)
    Hi, thanks for the reply, sorry if I'm being stupid but I don't really understand what to do with the electronegativity values now that I've got them. I got 3.16 for chlorine, 1.31 for magnesium and 1.61 for aluminium. I understand that aluminium and magnesium are both much less electronegative than chlorine but I don't really know how this works.
    They are both much less than chlorine, but whats important is that aluminium has a smaller difference, ionic bonds (without covalent characteristics) normally happen with elements that have a large difference in electronegativity. As the difference gets smaller, you get more characteristics of covalent bonding and less of ionic bonding.

    If you look at two extremes for example, an F-F bond has 0 difference in electronegativity and is perfectly covalent. If you had say an Na-F bond, there is a huge difference in electronegativity and the bond is very ionic. As you were to change the element bonded to F, the bond would shift between covalent and ionic, depending on how much the difference in electronegativity is.
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    (Original post by JN17)
    They are both much less than chlorine, but whats important is that aluminium has a smaller difference, ionic bonds (without covalent characteristics) normally happen with elements that have a large difference in electronegativity. As the difference gets smaller, you get more characteristics of covalent bonding and less of ionic bonding.

    If you look at two extremes for example, an F-F bond has 0 difference in electronegativity and is perfectly covalent. If you had say an Na-F bond, there is a huge difference in electronegativity and the bond is very ionic. As you were to change the element bonded to F, the bond would shift between covalent and ionic, depending on how much the difference in electronegativity is.
    Oh I see! Thank you very much! That was really helpful and really well explained!
 
 
 
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