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AS Chemistry Intermolecular Forces HELP! watch

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    ok SO THERE ARE:

    instantaneous-induced dipole attractions
    instantaneous-instantaneous


    are there induced-induced dipole attractions as well??

    :eek3:
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    Yes as an induced dipole can induce a dipole in it's neighbouring species.

    I think... but it is four years since I did Chemistry
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    (Original post by Coke Or Pepsi)
    ok SO THERE ARE:

    instantaneous-induced dipole attractions
    instantaneous-instantaneous


    are there induced-induced dipole attractions as well??

    :eek3:
    Induced is the same as instantaneous i thought but it was last year!! x x x
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    (Original post by Bubbalina)
    Induced is the same as instantaneous i thought but it was last year!! x x x
    Instantaneous isn't the same as induced :{ instantaneous is because the electrons move, so one part can be delta pos/neg, but induced is because a polar molecule causes the electron density to shift

    Also Bubbalina you also applied to BioMed (sorry for the irrelevance) but you applied to dentistry for the rest. I'm thinking of applying to BioMed as my 5th option, but doesn't that mean you have to change your personal statement to fit both courses? Or not? Thanks sorry again x


    (Original post by Spacecam)
    Yes as an induced dipole can induce a dipole in it's neighbouring species.

    I think... but it is four years since I did Chemistry
    That's what I thought but I can't find it anywhere :{
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    instantaneous-instantaneous interactions? :confused:
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    You mean permenant dipoles....they are a result of polarity



    The first one is non-polar (Cl-Cl) because both atoms in the molecule have the same electronegativity (electron pulling power) Electronegativity is determined by atomic radius, nucleus size etc. The most electronegative element is Fl...below in the general trend



    The second one is a polar bond, the Cl has greater electronegativity than hydrogen, therefore "pulls" electrons in the covalent bond towards it, this results in polarity. The part of the molecule where the electrons are pulled towards (in this case Cl) gets a negative charge because electrons are negative. And obviously the hydrogen will get a positive charge (protons are positive). This is permenant...therefore strong intermolecular bonds form between the + parts of molecules and - parts of molecules. These bonds are permenant, thus are stronger.
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    (Original post by EierVonSatan)
    instantaneous-instantaneous interactions? :confused:
    Yeah. Trust me, I'm as confused as you are.

    (Original post by Moe Lester)
    You mean permenant dipoles....they are a result of polarity



    The first one is non-polar (Cl-Cl) because both atoms in the molecule have the same electronegativity (electron pulling power) Electronegativity is determined by atomic radius, nucleus size etc. The most electronegative element is Fl...below in the general trend



    The second one is a polar bond, the Cl has greater electronegativity than hydrogen, therefore "pulls" electrons in the covalent bond towards it...

    Thanks for the help - but no I didn't mean permanent. Permanent is due to a difference in electronegativity. Induced is due to a polar molecule causing the electron density to shift in a non polar molecule, causing it to become polar. But I just want to know whether an induced species can induce another species thus forming a induced-induced dipole interaction.
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    (Original post by EierVonSatan)
    instantaneous-instantaneous interactions? :confused:
    I assume the OP must mean permenant dipoles which I attempted to explain above, could you possiby check it over, I'm still at AS level
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    (Original post by Coke Or Pepsi)
    Thanks for the help - but no I didn't mean permanent. Permanent is due to a difference in electronegativity. Induced is due to a polar molecule causing the electron density to shift in a non polar molecule, causing it to become polar. But I just want to know whether an induced species can induce another species thus forming a induced-induced dipole interaction.
    Ah obviously not :p: There is no such thing as induced-induced...induced-instantaneous surely, do you understand how they happen...electron clouds .etc. ?
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    (Original post by Moe Lester)
    I assume the OP must mean permenant dipoles which I attempted to explain above, could you possiby check it over, I'm still at AS level
    Permanent dipoles are different to instantaneous:

    Permanent = difference in electronegativity. Like in water; the oxygen is delta negative, and hydrogen delta positive. It's like that all the time, and it never goes away.

    Instantaneous is a type of temporary dipole.
    It comes about as a result of electrons moving and being in one part of the molecule/atom more frequently at any one time, causing an "instantaneous" dipole.

    (Original post by Moe Lester)
    Ah obviously not :p: There is no such thing as induced-induced...induced-instantaneous surely, do you understand how they happen...electron clouds .etc. ?
    Are you sure? Yeah I understand, but my logic behind it is that if there's an induced dipole, then surely that could induce another atom/molecule, forming another induced dipole, thus leading to a London bond being formed between the two induced dipoles.

    Ah this is so confusing -.-
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    (Original post by Coke Or Pepsi)
    Permanent dipoles are different to instantaneous:

    Permanent = difference in electronegativity. Like in water; the oxygen is delta negative, and hydrogen delta positive. It's like that all the time, and it never goes away.

    Instantaneous is a type of temporary dipole.
    It comes about as a result of electrons moving and being in one part of the molecule/atom more frequently at any one time, causing an "instantaneous" dipole.
    Yeah exactly, so how could something be induced-induced?

    There are only two types of Van der Waals forces

    1.) Force between permanent dipole and a corresponding induced dipole

    2.) instantaneous induced dipole-induced dipole (London dispersion force).
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    (Original post by Moe Lester)
    Yeah exactly, so how could something be induced-induced?

    There are only two types of Van der Waals forces

    1.) Force between permanent dipole and a corresponding induced dipole

    2.) instantaneous induced dipole-induced dipole (London dispersion force).

    Basically, as I said above, something can be induced because

    OK so you have a temporary dipole. The delta negative region repels the electron density of a neighbouring atom/molecule, causing it to shift and produce a induced dipole, forming an instantaneous-induced dipole bond.

    The induced dipole will go on to induce other neighbouring atoms/molecules, thus forming induced-induced bonds.

    BUT I can't find my logic anywhere, so I'm just trying to see if I'm correct or what :{ It's been eating my brain all day - my chemistry teacher is so hard to find!:yes:

    EDIT: the two are instantaneous-instantaneous (dispersion) and instantaneous-induced, i think :/
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    (Original post by Coke Or Pepsi)
    Basically, as I said above, something can be induced because

    OK so you have a temporary dipole. The delta negative region repels the electron density of a neighbouring atom/molecule, causing it to shift and produce a induced dipole, forming an instantaneous-induced dipole bond.

    The induced dipole will go on to induce other neighbouring atoms/molecules, thus forming induced-induced bonds.

    BUT I can't find my logic anywhere, so I'm just trying to see if I'm correct or what :{ It's been eating my brain all day - my chemistry teacher is so hard to find!:yes:
    No, forming more instantaneous-induced bonds.....
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    (Original post by Coke Or Pepsi)
    EDIT: the two are instantaneous-instantaneous (dispersion) instantaneous-induced:/
    No :p:

    http://www.chemguide.co.uk/atoms/bonding/vdw.html
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    Right, okay it's very easy to get muddled in terminology here :sadnod: Technically Van Der Waal forces is the umbrella term for all intermolecular interactions (though your A-level spec may say different)

    Instantaneous dipole-induced dipole interactions occur between all atoms/molecules with electrons and are weak for small molecules. One example is methane.

    Permanent dipole - permanent dipole interactions occur between molecules which have a permanent dipole. Propanone is one example of this

    Hydrogen bonds occur when a molecule has hydrogen attached to a very electronegative atom/group and there is a lone pair to accept a hydrogen bond. The classic example is water.

    Another one you may come across is permanent dipole - induced dipole...this is when a permanent dipole induces a temporary dipole on a non-polar compound. An example of this could be water and Cl2

    An 'induced-induced interaction' is an instantaneous dipole - induced dipole because the dipole created is temporary and not permanent - hope that makes sense :p:

    (There are some other interactions too but they're above A-level - such as ion-dipole and pi stacking)
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    Listen to him ^^
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    (Original post by EierVonSatan)
    Right, okay it's very easy to get muddled in terminology here :sadnod: Technically Van Der Waal forces is the umbrella term for all intermolecular interactions (though your A-level spec may say different)

    Instantaneous dipole-induced dipole interactions occur between all atoms/molecules with electrons and are weak for small molecules. One example is methane.

    Permanent dipole - permanent dipole interactions occur between molecules which have a permanent dipole. Propanone is one example of this

    Hydrogen bonds occur when a molecule has hydrogen attached to a very electronegative atom/group and there is a lone pair to accept a hydrogen bond. The classic example is water.

    Another one you may come across is permanent dipole - induced dipole...this is when a permanent dipole induces a temporary dipole on a non-polar compound. An example of this could be water and Cl2

    An 'induced-induced interaction' is an instantaneous dipole - induced dipole because the dipole created is temporary and not permanent - hope that makes sense :p:

    (There are some other interactions too but they're above A-level - such as ion-dipole and pi stacking)
    My course says different lol
    Edexcel

    It says that instantaneous is different to induced :/
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    (Original post by Coke Or Pepsi)
    It says that instantaneous is different to induced :/
    An instantaneous dipole is created instantaneously when 'there are more electrons on one side of the molecule than on the other' this is a temporary dipole. It is this temporary dipole that induces (causes) another temporary dipole on a near-by molecule leading to a interaction that joins them together.

    As I understand it, you're asking if a temporary dipole (which is induced) can interact with another temporary dipole (which is induced)? The answer is yes - but there is no difference between this temporary set up and the one described above.
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    (Original post by EierVonSatan)
    An instantaneous dipole is created instantaneously when 'there are more electrons on one side of the molecule than on the other' this is a temporary dipole. It is this temporary dipole that induces (causes) another temporary dipole on a near-by molecule leading to a interaction that joins them together.

    As I understand it, you're asking if a temporary dipole (which is induced) can interact with another temporary dipole (which is induced)? The answer is yes - but there is no difference between this temporary set up and the one described above.
    so basically induced-induced is the same as instantaneous-induced?
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    Use different words, it's what i did. Words that are different so you don't muddle them up!
    I don't know what exam board you're doing but these are the ones we had to learn:
    Van der Waals- present in all structures, very weak unless in giant structures, temporary dipole (small difference in electronegativity and it's only because electrons don't stay in one place and so move from one atom to the other at different points making each atom slighty negative and slighty positive (delta +/_) when it does so.
    Dipole-Dipole- this is permanent and occurs when one element is alot more electronegative than the other and the one which is more electronegative becomes (delta -) slighty negative and visa versa.
    Hydrogen bonding- occurs between H-N, H-O, H-F strongest of them all

    that's how AQA do it anyways...
 
 
 
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