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Thread: Change in electronegativity of an element

  1. #1
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    Change in electronegativity of an element

    Guys, consider this:
    en of an element is defined in its elemental state. if we consider the element in a compound, its electro-negativity depends on the other elements that it is bonded with. for example, if it is bonded to an element that is less en than itself, electron density around it increases thus decreasing its en in that compound. if it is attached to a more en element, its electron density decreases, making it more en. this works for many phenomenon, but, does such a theory relating to difference in en of an element in its compounds exist? if so, plz give me a link.
    thanks.

  2. #2
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    guys, please help out.

  3. #3
    Quote Originally Posted by rohIT View Post
    guys, please help out.
    QUOTE=rohIT;2929639]Guys, consider this:
    en of an element is defined in its elemental state. if we consider the element in a compound, its electro-negativity depends on the other elements that it is bonded withfor example,
    if it is bonded to an element that is less en than itself, electron density around it increases . ok
    thus decreasing its en in that compound. ok

    if it is attached to a more ( electro negative ? ) en element,
    its electron density decreases, Ok
    making it more en. this works for many phenomenon,

    but, does such a theory relating to difference in en of an element in its compounds exist? if so, plz give me a link.
    thanks.[/QUOTE]

    Look into organic compounds specially substitution in benzene rings > How electrowitdrawall ( elecronegative ) affect hydrogen replacement in the ring , or how electrodonor affect the ring for subsitution

  4. #4
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    Electronegativity reflects an atom's relative affinity for electrons. Usually the scale goes from 0 to 4, with F being 4.0. This relative scale helps us predict how atoms will interact with each other. The molecular bonding that might occur does not change the relative electro-negativity, since it is more useful as relative or comparative scale.

    If we have oxygen, hydrogen and carbon, the relative scale of electronegativity tells us that oxygen (3.5) will always want the electrons the most no matter how we combine these atoms. Carbon is always number two (2.5) and hydrogen (2.1) number three. This is useful for predicting structure and even the reactive spots in a molecule, no matter how complicated. You can draw electron arrows going to the oxygen (all roads lead to Rome).

    We can get single or double bonded oxygen to carbon, but in both case the oxygen (3.5) is still winning the electron tug of war with carbon (2.5). When oxygen and hydrogen combine, since oxygen (3.5) is even more electronegative than hydrogen (2.1) than carbon, oxygen often takes all the electrons of hydrogen allowing the hydrogen to leave as a proton. This is useful to acids.


  5. #5
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    @arauca
    yes, we actually thought of this when we were doing organic chemistry. it worked for everything we tried it on. it worked for all the inorganic compounds also (at least as many as we considered).

    @wellwisher
    consider inductive effect in which a long chain of carbons is attached to a highly en atom like F. F draws electrons towards itself thus reducing electron cloud density over C due to which it becomes more en. according to ur logic, the electrons between the successive C atoms must lie at the centre, which is definitely not the case. the electrons are attracted more by the C atom which is attached to the F causeing a permanent displacement of electrons.

    Guys, sorry for the late response. after waiting for fe days, i thought i wont get a reply. but, plz reply asap
    thanks.

  6. #6
    Are you looking for an equation that allows you to predict the EN of the atoms in the molecule? Such a thing does not currently exist. What you have to do at this point is look for compounds with a simular structure containing atoms with simular properties to the one that you have that have had their EN measured. This will not be 100% accurate but it will usually allow you to make an educated guess as to it's properties unless something novel is going on. Like how Ni, Pd, and Pt can form square planer compounds with 4 ligands where other metals will form a tetrahedral compound.

  7. #7
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    The concept of electronegativity is a compact tool used to compare the affinity of the various atoms for electrons. If we combined carbon and fluorine in a covalent arrangement (freon), the relative electronegativity tells us how the electron clouds will shift between the atoms based on which is higher or lower. This is a quick tool that allows us to infer many things based on ground states.

    Although the shift in the electrons, due to the fluorine, will alter the reactivity of the carbon, based on its new electron arrangement, this new state of carbon is an induced state and not a ground state. It cannot exist on its own, without help.

    The concept of electronegativity was designed to be a portable tool, like a swiss army knife. If we take carbon in every possible state of induction, as a separate "electronegative state", the little swiss army knife becomes more like a large tool box that is big to carry around.

  8. #8
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    nope. the thing will become more accurate. for many predictions...like in many cases in organic compounds on which we already ried this. and, u dont actually have to keep all these values with you. all you need is relative en of atoms, which already is a basic. from that, we can simply predict where the electrons will tend to go. we havent gone into its mathematics...we know not much of it (bpc students, lol). but this is helpful.
    guys, if anyone finds use of this in any molecule or system, plz give its formula and how u explained it using this. then probably we will come to know how many compounds this works for.
    and, they started teaching us complexes 2 or 3 days back. we were trying to explain the strong and weak ligands using this. will update if we come up with anything new
    thanks for your interest.

  9. #9
    Quote Originally Posted by rohIT View Post
    nope. the thing will become more accurate. for many predictions...like in many cases in organic compounds on which we already ried this. and, u dont actually have to keep all these values with you. all you need is relative en of atoms, which already is a basic. from that, we can simply predict where the electrons will tend to go. we havent gone into its mathematics...we know not much of it (bpc students, lol). but this is helpful.
    guys, if anyone finds use of this in any molecule or system, plz give its formula and how u explained it using this. then probably we will come to know how many compounds this works for.
    and, they started teaching us complexes 2 or 3 days back. we were trying to explain the strong and weak ligands using this. will update if we come up with anything new
    thanks for your interest.
    Nope to what exactly?

    Also, I as I said above there is no equation for this because it is rather unpredictable. You can get somewhat close, but there are many, many different factors that can effect the reactivity of any one atom in a compound. The only way you can kind of predict it is by compairing it to a simular structure that is already measured, but this is not an exact science as there are many novel mechanisms that kick in at unknown threshholds. (I.E. We know this mechanism kicks in over a range from 2-5 but not always as in if your at 3.5 it's not guarenteed to happen, but at 5 it is)

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