Thread: Chemistry questions

  1. #1
    Back after 2 years Panopticon's Avatar
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    Chemistry questions

    On my homework, I came across a reference to a molecule with a formulae of XeF4. Is such a molecule possible? or is my teacher mistaken..
    And how is NO2 bonded? Nitrogen has 3 available covalent bonds while Oxygen has 2. Is this case similiar to that of CO where co-ordinate covalencies are involved or what? I've tried drawing diagrams for the bonding structure (without co-ordinate covalent bonds) and still haven't found a possible case where N and O can exist as NO2 (Or NO for that matter)... woe is me.
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    The Earth is not flat. Clyde's Avatar
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    On my homework, I came across a reference to a molecule with a formulae of XeF4. Is such a molecule possible? or is my teacher mistaken..
    And how is NO2 bonded? Nitrogen has 3 available covalent bonds while Oxygen has 2. Is this case similiar to that of CO where co-ordinate covalencies are involved or what? I've tried drawing diagrams for the bonding structure (without co-ordinate covalent bonds) and still haven't found a possible case where N and O can exist as NO2 (Or NO for that matter)... woe is me.
    XeF4 is a real molecule, as is NO2, CO, and a whole host of other molecules.

    The faff answer is you use dative covalent bonds:

    In CO carbon needs 4 and oxygen needs two, they form a double bond by sharing two electrons each giving oxygen its full outer shell and leaving carbon still needing two more, so oxygen lets carbon share two more of its electrons, thats a dative covalent bond.

    NO2 you can represent as a one neutral oxygen double bonded and once negative oxygen single bonded to a positive nitrogen. Use normal rules then add an electron to the negative oxygen and remove one from the positive nitrogen.

    The real answer is that chances are, almost everything you have been taught about bonding is utter nonsense: All the stuff you have done on ionic bonding (those circle diagrams) is complete nonsense and what you understand of the entire driving force behind chemical reactions - the octet or "full outer shell" rule is not the be all and end all that it is presented as at your level.
    Last edited by Clyde; 06-03-2003 at 04:59 AM.

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    Back after 2 years Panopticon's Avatar
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    Yeah just as I suspected, dative bonds. (Dative bonds are another name for co-ordinate covalent bonds apparently) Seems like that would be the only way those mentioned molecules could exist.

    The real answer is that chances are almost everything you have been taught about bonding is utter nonsense: All the stuff you have done on ionic bonding (those circle diagrams) is bogus and what you understand of the entire driving force behind chemical reactions - the octet or "full outer shell" rule is also all lies.
    Well, my "chemistry" teacher is an idiot that can't read the periodic table, and is actually a biology teacher which imo shouldn't be considered a science. (and I question his ability in that field too) See, because of that I've taken the initiative to tutor myself on the sciences from text books. Now, what you're saying is the books I'm using are wrong? That's a pretty big statement.

    Either way, thanks for confirming my suspicions
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    The Earth is not flat. Clyde's Avatar
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    "I've taken the initiative to tutor myself on the sciences from text books. Now, what you're saying is the books I'm using are wrong? That's a pretty big statement."

    The way chemistry is taught at pre-undergrad levels is amazingly simplified to such an extent that it's essentially nonsense.

    Ok, not all of it, at levels just pre-undergrad (A-Levels in England) its starts getting a bit better.

    So yea alot of whats in your books is "wrong" but then the authors know this and wrote them "wrong" deliberately so that they would be easier to understand.
    Last edited by Clyde; 06-03-2003 at 05:09 AM.

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    Back after 2 years Panopticon's Avatar
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    Oh ok I see, point taken.
    Yeah, I'm starting to realise alot of stuff is made gibberish for the sake of simplicity, but they do serve as a healthy foundation for deeper concepts that are to come at higher levels of study, simply because the bs learnt before would in most cases require small alterations to suit the current teaching. I see your point.

    Well, personally I'm not really a chemistry person anyway, only taking chem cos its a science and I'm naturally good at understanding concepts (well, compared to my ineptitude in English, which here is sadly a compulsory subject thats downright pulling my beautiful marks down ) I'm more into physics, but then again, at a high school level they teach physics as its name implies "physics" as general as it comes. We learn the basics of everything. hehe I like rambling.
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    Much older and wiser Fountain's Avatar
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    Why is biology not a science?

    Or did you mean like at school level or something. It is kinda important subject and may lead to ppl studying medicine/chemistry etc etc. Or is it just the 'word' biology you dont believe is a science?
    Such is life.

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    Originally posted by Panopticon
    Oh ok I see, point taken.
    Yeah, I'm starting to realise alot of stuff is made gibberish for the sake of simplicity, but they do serve as a healthy foundation for deeper concepts that are to come at higher levels of study, simply because the bs learnt before would in most cases require small alterations to suit the current teaching. I see your point.

    Well, personally I'm not really a chemistry person anyway, only taking chem cos its a science and I'm naturally good at understanding concepts (well, compared to my ineptitude in English, which here is sadly a compulsory subject thats downright pulling my beautiful marks down ) I'm more into physics, but then again, at a high school level they teach physics as its name implies "physics" as general as it comes. We learn the basics of everything. hehe I like rambling.
    no no you dont understand... what you learn is completly useless and has not been used since the 1800's in most cases... and most of it is completly irrelevant to the current theories...

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    >>I've taken the initiative to tutor myself on the sciences from text books<<

    Perhaps an introduction to Molecular Orbital theory may be of interest:

    http://www.chm.davidson.edu/Chemistr...als/index.html

    http://www.ch.ic.ac.uk/vchemlib/cour...eory/main.html

    http://www.chem.qmul.ac.uk/software/download/mo/

    A little group theory (molecular symmetry) is always useful too:

    http://www.chem.wm.edu/courses/chem402/hand.html

    http://www.science.siu.edu/chemistry...eory/sym1.html

    >>...not been used since the 1800's in most cases...<<

    Was it as long ago as that? Just seems like yesterday...

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    Back after 2 years Panopticon's Avatar
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    Thanks for the feedback ppl, really helps.

    Why is biology not a science?
    Well personally I have nothing against the study as a science itself, I guess I wasn't thinking straight in my haste when I typed. My opinion though is that people (in my school anyway) that take biology ........ me off cos you cud just tell by their behaviour that hey have no passion for the sciences, and merely taking it cos they are (most, no, vast majority) mindless mediocre drones void of individual thought that go by the cliche that "doctors get paid alot and i like money, therefore i'll take biology!".
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    Originally posted by Clyde
    "I've taken the initiative to tutor myself on the sciences from text books. Now, what you're saying is the books I'm using are wrong? That's a pretty big statement."

    The way chemistry is taught at pre-undergrad levels is amazingly simplified to such an extent that it's essentially nonsense.
    Holy $$$$!

    I'm ........ed off now. Everything I've been taught is bull$$$$? That is $$$$ing gay. Means I'll have to relearn it all at $$$$ing chemistry A Level. If people weren't so $$$$ing retarded, maybe they'd teach us the real deal rather than a bunch of lies. 8 electrons in the outer shell my ass.

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    erstwhile
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    >>Everything I've been taught is bull$$$$?<<

    As Clyde has pointed out it's a 'simplified' version ie texts are "...wrong" but then the authors know this and wrote them "wrong" deliberately..."

    There are historical and utilitarian reasons for this - for many practical purposes this 'simplified' or conventional approach works perfectly well and so a 'it's good enough to get the job done' attitude is taken. For example, consider what you have learned in Chemistry so far: you are able to predict with some precision and certainty the paths, states and outcomes of many reactions using these 'older' models.

    Here's an analogy: consider the expressions "the sun comes up" or "sunrise". These expressions exist for historical reasons, before understanding of the motions of Earth and Sun were properly understood. We retain - and understand - these expressions because they 'seem' to be true; they have sufficient utility and practicality in our everyday lives so that there is no need, at that level of understanding, to alter them or their use even though we know that they are actually false statements.

    Anyway, if you think that's bad, consider the plight of electronic engineers who, by convention and for pretty much the same historical reasons, use positive current flow.

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    Yeah, but they could have at least told us, "this isn't true, but..."

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    Well I'm in tenth grade and my honors chemistry teacher was ACTUALLY a chemist! He worked on lasers. Anyways, we were taught things beyond the textbook and things that other chemistry teachers don't know how to do.

    But in bonding, we were taught about the s, p blocks, hybrid orbitals, exceptions to the octet rule, and all this crazy stuff. Seems really real and I understand why many of these molecules bond and how and which "slots" are open for more bonds.

    So it all depends on your teacher.

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    Originally posted by Speedy5
    Well I'm in tenth grade and my honors chemistry teacher was ACTUALLY a chemist! He worked on lasers. Anyways, we were taught things beyond the textbook and things that other chemistry teachers don't know how to do.

    But in bonding, we were taught about the s, p blocks, hybrid orbitals, exceptions to the octet rule, and all this crazy stuff. Seems really real and I understand why many of these molecules bond and how and which "slots" are open for more bonds.

    So it all depends on your teacher.
    yeah a laser! that is proof he is a chemist that would actually have more to do with physics...

    and trust me the stuff you learnt was not what is currently used by chemists...

    not to mention the whole high school level bonding theory is bogus...

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    Toaster Zach L.'s Avatar
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    Originally posted by ZerOrDie
    and trust me the stuff you learnt was not what is currently used by chemists...

    not to mention the whole high school level bonding theory is bogus...
    True true, but then again, so many things are like that. Take physics as an example. Just about every school starts out teaching Newtonian physics, as opposed to more recent theories such as Relativity.
    The word rap as it applies to music is the result of a peculiar phonological rule which has stripped the word of its initial voiceless velar stop.

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