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    "In the gaseous phase aluminium chloride, AlCl3 exists as the dimer Al2Cl6. Explain how two AlCl3 molecules are linked together."

    I don't know whether the answer is Ionic Bonding or Van der Waals?
    Could somebody explain which one it is, why it is so, and why it is not the other

    thanks!
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    Two dative covalent bonds are formed.

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    first of all make sure you understan this is a COVALENT STRUCTURE not an ionic one

    it looks like this:

    ............Cl
    .............|
    ......Cl - Al - Cl
    .............|.....|
    ............Cl - Al - Cl
    ...................|
    ..................Cl

    The 2 lines in bold are DATIVE COVALENT BONDS - i.e. a lone pair of electrons in the outer shell of Cl is being shared with the Al in order to give each Al 8 electrons in its outer shell, which makes it more energetically stable
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    (Original post by conzag123)
    first of all make sure you understan this is a COVALENT STRUCTURE not an ionic one

    it looks like this:

    ............Cl
    .............|
    ......Cl - Al - Cl
    .............|.....|
    ............Cl - Al - Cl
    ...................|
    ..................Cl

    The 2 lines in bold are DATIVE COVALENT BONDS - i.e. a lone pair of electrons in the outer shell of Cl is being shared with the Al in order to give each Al 8 electrons in its outer shell, which makes it more energetically stable
    ahh I would never have got that.
    is there any way to recognise dative covalent bonds?
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    (Original post by KingofSpades)
    ahh I would never have got that.
    is there any way to recognise dative covalent bonds?
    there's not really nay way of knowing when dative covalent bonds are used unfortunately.

    At A level you're told there used in the structures of the ammonium ion (NH4+), the carbonate ion (CO3 2-) and the sulfate ion (SO4 2-), though these are simplifications in fact but don't you worry about that!

    Just remember this case (aluminium chloride dimer) or similar cases (ie. boron chloride OR aluminium fluoride etc) as well as the NH4+ ion and then you should be fine
 
 
 
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