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chloride ions are bigger than h2o

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    I used to think its the other way around! is there any reason why cl is bigger?



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    Can you provide a source that confirms what you've said ?
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    (Original post by arvin_infinity)
    I used to think its the other way around! is there any reason why cl is bigger?



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    I think we can't just easily compare a monatomic ion with a neutral molecule. The modern techniques are used to determine their size. According to my book, chloride ions are bigger than water molecules. A proof of this comes from transition metals chemistry. Whenever a [Cu(H2O)6]2+ ion reacts with Chloride ions from HCl, the six water ligands are replaced by 4 chloride ligands because chloride ions occupy more space than water molecules.
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    (Original post by Ari Ben Canaan)
    Can you provide a source that confirms what you've said ?
    Cl ions are bigger than H2o molecules ! just wondered why
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    (Original post by Zishi)
    I think we can't just easily compare a monatomic ion with a neutral molecule. The modern techniques are used to determine their size.
    Yh I wasn't asking if someone can measure it and tell me how different they are!
    Just thought maybe there is an explanation as to why its bigger!


    According to my book, chloride ions are bigger than water molecules. A proof of this comes from transition metals chemistry. Whenever a [Cu(H2O)6]2+ ion reacts with Chloride ions from HCl, the six water ligands are replaced by 4 chloride ligands because chloride ions occupy more space than water molecules.
    oh yeh my book says the exact same thing!
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    Remember chloride ions have an extra electron when compared to the atom and a whole new shell compared to O. This increases the ionic radius significantly - it has a larger effect than the increasing nuclear charge going from O to Cl. H atoms are tiny - if you've seen (or go and find) a space filling diagram of any hydrogen containing molecule you'll see what I mean.

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    (Original post by arvin_infinity)
    I used to think its the other way around! is there any reason why cl is bigger?



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    If you assume that hydrogen does not contribute significantly to the size (see below) then:

    oxygen ionic radius 126pm
    chlorine ionic radius: 167pm
    (www.chemcool.com)

    Oxygen has an ionic configuration 2,8 while chloide has a configuration 2,8,8. It is the result of an entirely new shell which makes it bigger.

    However, O-H bond lengths (nuclear centre to nuclear centre) are about 90pm. This means that hydrogen effectively does not add to the radius of the oxide ion.

    This data suggests that the diameter of a water molecule does not exceed 180pm while the diameter of a chloride ion is 334pm, nearly twice the size.

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Updated: April 17, 2012
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