• Researchers redefine the rules of chemistry
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[quote] Research by a Northumbria academic could have a significant impact on the teaching of chemistry after he developed a radical new interpretation of a 99-year-old rule featured in all standard textbooks. Dr Marcus Durrant, a Reader in Northumbria's Department of Applied Sciences, realised that the treatment of hypervalency in the Lewis theory of chemical bonding was flawed while he was teaching the theory to students. The Lewis model, which was first published in 1916, features in every elementary chemistry textbook and has been taught to generations of chemists. It states that a nitrogen atom cannot have five covalent bonds, as this would break the 'octet rule' which is a central part of Lewis' theory. However, the subject has been the matter of some dispute since the 1990s, when quantum calculations showed that the chemical bonds in nitrogen compounds are no different to those formed by heavier elements such as phosphorus, which often break the 'octet rule'. "We continue to teach this convention even though the theory behind it was shown to be wrong 25 years ago. Some chemists have even suggested that the term 'hypervalent' should be abandoned altogether, even though it is still in widespread use. I was musing over this after discussing these problems in the classroom and decided to explore whether there was a way to settle the controversy. Read more at: [url]http://phys.org/news/2015-09-redefine-chemistry.html#jCp[/url] [/quote] OK so chemistry isn't going to stop working or anything, but i always thought some of the arbitrary-ness around some of the unique cases in chemistry may have just been because we couldn't explain these things adequately, anyways if i read this right, the octet rule got a little stronger
but what does this mean all in all? [sp]never actually took chem[/sp]
:johnnymo1:
That's a hell of a title, but what does it actually meant in practical effect?
Basically some compounds that are classically thought to be impossible probably aren't impossible. The headline is also misleading. We've known this for forty-five years now, and we regularly produce hypervalent compounds. We just still teach the octet rule in schools because it's mostly accurate, especially for the stable molecules most chemistry deals with.
[QUOTE=J!NX;48722245]but what does this mean all in all? [sp]never actually took chem[/sp][/QUOTE] the way things are taught is that nitrogen will only ever make 4 covalent (sharing electrons) bonds with other atoms. research shows that it might be able to make more, so textbooks would need to be changed
[QUOTE=Javelin;48722427]That's a hell of a title, but what does it actually meant in practical effect?[/QUOTE] it means chemistry may have gotten a little more organized, thats about it.
[QUOTE=capital;48722449]the way things are taught is that nitrogen will only ever make 4 covalent (sharing electrons) bonds with other atoms. research shows that it might be able to make more, so textbooks would need to be changed[/QUOTE] [QUOTE=gman003-main;48722443]Basically some compounds that are classically thought to be impossible probably aren't impossible. The headline is also misleading. We've known this for forty-five years now, and we regularly produce hypervalent compounds. We just still teach the octet rule in schools because it's mostly accurate, especially for the stable molecules most chemistry deals with.[/QUOTE] so what this really means; is that text books are almost half a century out of date
[QUOTE=gman003-main;48722443]Basically some compounds that are classically thought to be impossible probably aren't impossible. The headline is also misleading. We've known this for forty-five years now, and we regularly produce hypervalent compounds. We just still teach the octet rule in schools because it's mostly accurate, especially for the stable molecules most chemistry deals with.[/QUOTE] outside of the actual paper, the article seems to suggest that the octet rule does apply to hypervalent compounds, we just were not measuring things correctly idk, but from a practical standpoint, better understanding hyper valency means better modeling of compounds, someday we'll be able to completely predict chemical properties before we synthesize them
[QUOTE=J!NX;48722462]so what this really means; is that text books are almost half a century out of date[/QUOTE] essentially. octet rule is really convenient way to estimate things and holds true a good majority of the time so I don't see it going away for a while.
[QUOTE=J!NX;48722462]so what this really means; is that text books are almost half a century out of date[/QUOTE] Hypervalent compounds are relatively exotic chemistry. Teaching the octet rule in high-school chemistry is probably a good thing - it lays the foundation for the weirder stuff. Most students wouldn't be able to handle learning all of it at once, and the octet rule is good enough for layman chemistry. Obviously the college-level chemistry textbooks go further. It's like how we teach Newtonian gravity in school. Relativity is technically more accurate but you don't need that most of the time.
[QUOTE=gman003-main;48722491]Hypervalent compounds are relatively exotic chemistry. Teaching the octet rule in high-school chemistry is probably a good thing - it lays the foundation for the weirder stuff. Most students wouldn't be able to handle learning all of it at once, and the octet rule is good enough for layman chemistry. Obviously the college-level chemistry textbooks go further. It's like how we teach Newtonian gravity in school. Relativity is technically more accurate but you don't need that most of the time.[/QUOTE] by newtonian do you mean just that "what goes up must come down?" because that is about as far as my highschool classes ever got.
Yeah this isn't really groundbreaking. When I took ochem, the professor said a ton that the octet rule isn't always correct but often it is and unless you go really far with chemistry that specifies with these rule breaks which are still not common, it would be tedious to learn all the different special cases.
isn't more of basic chem "general rule" kinda stuff anyway
It's like when you learn a language and they say "This rule works for everything this way grammatically, except for all of these cases." And then there's a list of like every other word in the language. It's an approximation of what will most likely happen, but atoms are finicky and interaction is not set in stone by the octet rule.
Hypervalency is actually looked at in highschool chemistry. Almost all of the polyatomic ions you learn are hypervalent.
[QUOTE=Xain777;48722725]by newtonian do you mean just that "what goes up must come down?" because that is about as far as my highschool classes ever got.[/QUOTE] Newtonian as in something that's fixed and can be done on paper straight forward, relativity is huge, clunky and requires lots of time to do for something that outside of a few applications doesn't add anything. I had a professor demonstrate this once, he did the relativity math and the Newtonian math and showed the error is non existent for most cases. It's also why ideal gas laws or modified ideal gas laws are taught, because it holds true in ordinary conditions and can be easily done, you don't want to use fugacity coefficients ever
A lot of basic chemistry is pretty much straight up wrong but we teach it because it's close enough. Orbital shells is a big one. Lewis dot is useful but honestly if you're doing higher level chemistry you'd want to stick to Molecular orbital diagrams instead. It's a big more useful since you can work out paramagnetism and shit as well. [editline]20th September 2015[/editline] Chem is riddled with shit that doesn't make sense. Especially fucking organic chemistry.
How is this news? Hypervalency is a non-issue in the molecular orbital treatment of bonding. It's been a non-issue for the past half century or so.
[QUOTE=The Aussie;48722969]A lot of basic chemistry is pretty much straight up wrong but we teach it because it's close enough. Orbital shells is a big one. Lewis dot is useful but honestly if you're doing higher level chemistry you'd want to stick to Molecular orbital diagrams instead. It's a big more useful since you can work out paramagnetism and shit as well. [editline]20th September 2015[/editline] Chem is riddled with shit that doesn't make sense. Especially fucking organic chemistry.[/QUOTE] Organic chemistry makes more sense than inorganic.
[QUOTE=gman003-main;48722443]Basically some compounds that are classically thought to be impossible probably aren't impossible. The headline is also misleading. We've known this for forty-five years now, and we regularly produce hypervalent compounds. We just still teach the octet rule in schools because it's mostly accurate, especially for the stable molecules most chemistry deals with.[/QUOTE] Not to mention with chemistry especially shit changes all the time.
Misleading title, this is only about how there are exceptions to the octet rule but everyone knows that
When I was taught Lewis' theory a couple of years ago, it was very clear that it was not supposed to be 100% precise, and only a clarification. Atoms can bond as long as they have free electrons, although it varies. Shit's complex.
[QUOTE=J!NX;48722462]so what this really means; is that text books are almost half a century out of date[/QUOTE] I mean, not any more than high school textbooks teaching Newtonian mechanics instead of general relativity are out of date. [editline]20th September 2015[/editline] [QUOTE=BFG9000;48722362]:johnnymo1:[/QUOTE] What do I look like, some kind of chemist?
[QUOTE=JohnnyMo1;48724191]I mean, not any more than high school textbooks teaching Newtonian mechanics instead of general relativity are out of date. [editline]20th September 2015[/editline] What do I look like, some kind of chemist?[/QUOTE] You say that as if being a chemist is a bad thing :(
[QUOTE=Xain777;48722725]by newtonian do you mean just that "what goes up must come down?" because that is about as far as my highschool classes ever got.[/QUOTE] By Newtonian I mean: F=G*m[1]*m[2]/r^2 (which is what I learned in high school) Instead of: R[μν]-R*G[μν]/2+Λ*G[μν] = (8*π*G)/(c^4)*T[μν] (the math for which I still don't know, because tensors are pretty high-level calculus)
[QUOTE=gman003-main;48724573]By Newtonian I mean: F=G*m[1]*m[2]/r^2 (which is what I learned in high school) Instead of: R[μν]-R*G[μν]/2+Λ*G[μν] = (8*π*G)/(c^4)*T[μν] (the math for which I still don't know, because tensors are pretty high-level calculus)[/QUOTE] damn, I just realized you said almost exactly what I said three posts ago earlier in the thread
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