List of Chemistry Exceptions

[escape_velocity]

Many years ago I started a list of zoological exceptions that's now hundreds of items long, so I was bound to notice the exceptional cases when I started to go over my long-forgotten knowledge of chemistry just four months ago. If so many have piled up in such a short period of time then surely there must be many others that only the advanced students or the pros are aware of. This is an invitation to add them to the following list.

 

I doubt that it would ever grow to be as long as the other one, to which additional facts are frequently being added, or even as long as a much shorter one of botanical exceptions. I've been an amateur astronomer ever since 1985 and I have piles of notebooks but astronomy offers no notable amount of exceptional cases. Biology itself has turned out to be unique as far as exceptions are concerned. Not included are a set of exceptions having to do with metallurgy, which I suppose is in a somewhat different category, and two abstruse ones about the color phenomenon.

 

1) ONLY chemical element with no neutrons in the nucleus (or more exactly, "whose common isotope has no etc.", since both deuterium and tritium do): hydrogen

 

2) ONLY element in Group 18 (or Group 0), the "inert" gases, that doesn't have eight outer electrons: helium

 

3) ONLY halogen that doesn't combine to give oxyhydrogenated acid compounds: fluorine

 

4) "inert" elements (or how should this be worded, since they're not entirely so --maybe "largely inert"?)

 

5) nonmetallic elements with less than five outer electrons: ONLY hydrogen, helium and carbon

 

6) nonmetallic elements that don't make compounds by gaining or sharing electrons: ONLY the "inert" elements

 

7) elements on the upper right-hand corner of the table that are not among the most reactive: ONLY the ditto

 

8) elements on the far right that don't have a very high electronegativity: ONLY the ditto

 

9) elements whose atomic mass doesn't agree with the sequence of increasing atomic numbers: ONLY potassium, nickel and iodine

 

10) cases where the oxidation number is not a periodic property

 

11) compounds in which oxygen doesn't have -2 as the oxidation number

 

12) hydrogenated compounds in which the oxidation number of hydrogen is not +1

 

13) oscillating chemical reactions (see "Scientific American", 3/83)

 

14) amino acids (ONLY two) with atoms of elements other than carbon, hydrogen, oxygen and nitrogen

 

15) solids that dissolve exothermically

 

16) crystalline polymorphism

 

17) substances in whose phase diagram the S-L line leans towards the left as pressure increases

 

18) cases where the reticular energy and the hydration energy are approximately equal

 

19) crude oils (petroleums) with components having carbon rings: ONLY Caucasian crudes

 

 

[John Cuthber]

You can cross out #3

http://en.wikipedia.org/wiki/Hypofluorous_acid

[WorldOfBiochemistry]

Interesting post.

[insane_alien]

and 5 silicon has 4 outer electrons.

 

to be honest I think the whole thing is pointless, there are no exceptions to the actual rules. There are however exceptions to the simplified rules of thumb, but thats because they are rules of thumb and not actual rules.

[mississippichem]

and 5 silicon has 4 outer electrons.

 

to be honest I think the whole thing is pointless, there are no exceptions to the actual rules. There are however exceptions to the simplified rules of thumb, but thats because they are rules of thumb and not actual rules.

 

Yeah, these are more "rules of thumb" than actual rules. The only real rules in chemistry are the laws of physics and mathematics.

 

In theory all chemistry can be derived out of QM and SM. However, no one knows how to solve an equation with that many variables or parameters.

[hypervalent_iodine]

I would cross out 6 also. I assume by 'inert' you refer to the noble gases? Xenon, for instance, has been known to form hypervalent compounds since the middle of last century.

 

You might also cross out 14, or at least redefine it to include only the 20 standard amino acids.

[mississippichem]

I would also say that number 10 is not an exception as the d and f blocks comprise most of the periodic table and only VERY loosely follow a periodic trend of most common oxidation state. Crystal field effects almost always win out.

[escape_velocity]

Pra WorldOfBiochemistry: obrigadissimo! (Your Evoluciencia website is now on my Favorites Bar so I won't miss any recent scientific news.)

 

" (…) the whole thing is pointless, there are no exceptions to the actual rules." --insane_alien

 

"Yeah (…)." --mississippichem

 

Those two quotes deserve this counterquote: "Science admits no exceptions; otherwise there would be no determinism in science, or rather, there would be no science." (Leçons de Pathologie Expérimentale [1872], Claude Bernard [the French physiologist])

 

The nature of the list is being misunderstood. It wasn't presented as exceptions to any of the iron laws of Nature, which are etched in marble and are not supposed to have exceptions except when overruled by supernatural causes, but merely as a series of unusual or curious circumstances that disrupt a pattern --a pattern that may or may not be contrived and forced rather than one that obeys a natural decree. Such a list might be of some use or entirely useless, but what's certain is that some people are not amused.

 

Some of the mistakes might be ascribed to the fact that the books I'm using are quite old. My chemistry textbook is from the early 60's. Moreover, item # 19 was found in the third edition (1948) of The Petroleum Handbook (Shell), so it's possible that other crudes that have carbon rings have been found. There has got to be at least one petroleum engineer amongst the nearly 40,000 members here who can help us out on this matter.

 

Incidentally, I'm not supposed to have that book, which seems to be a FOR-YOUR-EYES-ONLY type of printed matter. On the other side of the title page it says "FOR PRIVATE CIRCULATION". I keep wondering how it ever got to the used-book market. I'm not in the industrial-espionage trade. Still, something else I keep wondering is what price it would fetch at an auction sale or a place like e-Bay. I bought it dirt-cheap, for the equivalent of about one U.S. dollar. Those who were selling it had no idea about what they had on their hands. It was as though they wanted to get rid of it after years of having it on the shelf.

 

(By the way, that first quote up there is a run-on sentence.)

 

"You can cross out # 3." --John Cuthber

 

…but one new exception will compensate for that loss. It happens to be mentioned on the Wiki entry on the compound HOF you furnish the URL to: "It is the only hypohalic acid that can be isolated as a solid." Thank you for making a contribution to the list.

 

" (…) number 10 is not an exception as the d and f blocks comprise most of the (…) table (…)." --mississippichem

 

In that case then the exception would have to be the complete opposite: "cases where the oxidation number is a periodic property". Or not. It depends on how you handle the terms "most" and "exceptional". Transition elements (d- and f-blocks) make up 63 % of the table. Can a feature displayed by the remaining 37 % of anything be described as "exceptional"? Not if you agree with the statistic definition of "normal" in psychology and decide to apply it to chemistry (there are two other definitions of the word in that science): "whatever two thirds of people do". That makes 33 % the maximum of "abnormality", so that 37% would be beyond the realm of the abnormal and thus not strictly abnormal or exceptional. Alternately, you can embrace the transitionals as the paragon and treat all the rest as circus freaks, but would it be fair….

 

" (…) cross out 14, or at least redefine it to include only the 20 standard amino acids." --hypervalent_iodine

 

So let's redefine. Also, while researching this I came across two other exceptional cases:

 

- ONLY naturally occurring beta amino acid: beta-alanine

 

- ONLY amino acid with the ability to easily cross the barrier between blood and brain tissue: glutamine

 

" (…) QM and SM." --mississippichem

 

Quantum mechanics? At least one can be sure that "SM" is not "sadomasochism" in the present context.

 

" (…) no one knows how to solve an equation with that many variables (…)." --mississippichem

 

Solve an equation??? What variables???

 

All one can say about this is that it recalls the "problem of n bodies" or "problem of multiple bodies". The mathematical difficulties are insurmountable. It pops up when wanting to describe the movement of a planet under the influence of all the others. Mechanics has no math tools for that yet, so you have to use a computer, a brute-force algorithm and a purely numerical method…but the memory requirements for one such program are gigantic. This is the method of the successive approximations. Discussing it goes beyond the scope of this forum unless you see any similarities to what you're talking about and it can be used for chemistry problems, too. (There's also the analytic approach --the method of the disturbances.)

 

 

 

 

 

 

 

 

 

[hypervalent_iodine]

Might I suggest getting a newer text book, or at least using the internet to check your information? A lot has happened since the 1960's.

[mississippichem]

escape_velocity: SM refers to statistical mechanics. I was trying to say that a list of chemistry exceptions pointless in the sense that its always a bit subjective, and not too useful. We could say that chromium and copper are the only two elements in the first row of the d-block that don't follow the ground state neutral charge orbital filing pattern, but really there is no exception here. There is a well known underlying cause for this phenomenon. It has to do with shielding, orbital penetration and all this coupled with a specific nuclear charge.

[escape_velocity]

"A lot has happened since the 1960's." --hypervalent_iodine

 

Yes, like chemist and Nobel-Prize winner Linus Pauling announcing to all of humankind that the common cold was avoidable by simply eating lemons daily and in large quantities, and then they told us this was nonsense. (Maybe he was ultimately responsible for the megavitamin trend.) I didn't need to have a Ph.D. to discover the solution: just stop using antibiotics, which weaken your immunological system and make it lazy.

 

I replaced them with...table salt! Humble NaCl is a powerful bug killer, as they found out thousands of years ago. It will even destroy what no antibiotic can: viruses. Specifically, it will instantly desensitize the common, small and painful mouth ulcers called "aphthae" or "thrush", caused by a herpes type of virus. If you keep putting salt on the sore it will go away quickly. Why does nobody seem to know about this? I had to figure it out all by myself and it will work again and again.

 

Not only that, but salt will make (external) ear infections and sore throats go away, too. I've been at it for the last three decades. In my case most episodes of influenza now last for about half an hour or so. They got shorter and shorter over the years. All of a sudden there's some sneezing, maybe mild pain in an eye socket and the temple on that same side and a runny nose, and then it's gone. In fact, the fleeting event is fun (especially the sneezing), as it breaks the routine. May I suggest that I be nominated for the Nobel Prize for medicine? These findings are earth-shaking and salt-shaking and maybe even life-saving.

 

If doctors and drug companies won't preach the gospel then maybe chemists will. There's more to it, having to do with tropical ulcers (not mine!), but the subject here is old books. Another old textbook I saw at a used-book fair was Pauling's chemistry textbook. I almost rushed to buy it but then I saw that an entire chapter had been ripped out and I walked away. I should've bought it, in spite of iodine's suggestion to modernize.

 

" (...) a list of chemistry exceptions is pointless in the sense that it's always a bit subjective, and not too useful." --mississippichem

 

Both a fondness for old books and collecting exceptions can become an obstacle in the way and it can turn into compulsive behavior, like anorexia and bulimia…yet I've come up with at least one good use for the pointless list: a didactic one. Teachers can announce a contest where the winner will be the student who can find the most exceptions having to do with the Periodic Table. The winner won't have to take the final exam.

 

Anyway, let these be my parting words: I hereby threaten to come back with more exceptions as soon as they go beyond the hundredth item, if ever, and I challenge those with enough spare time on their hands to beat me to it. I'm grateful to those who pointed out all the mistakes.

 

It's back to the salt mines, then (i.e., the textbooks).

 

 

[John Cuthber]

"I didn't need to have a Ph.D. to discover the solution: just stop using antibiotics, which weaken your immunological system and make it lazy. "

Bollocks; colds were around before antibiotics and there's no evidence they make the immune system lazy (whatever that might mean).

 

"Specifically, it will instantly desensitize the common, small and painful mouth ulcers called "aphthae" or "thrush", caused by a herpes type of virus"

Bollocks. Thrush is caused by a fungus and while aphthae may be caused by a virus, they are just as likely to be bacterial.

 

" If you keep putting salt on the sore it will go away quickly"

If you don't it will too. Salt may reduce the duration. In my experience vodka on a bit of cotton wool works too. More or less any antibacterial is in with a chance here; perhaps someone would like to try honey.

 

"Why does nobody seem to know about this? "

One possibility is that they think it's bollocks.

" In my case most episodes of influenza now last for about half an hour or so. "

If that was even close to true you would get the Nobel prize for medicine.

What is much more likely is that, like me, you have the good fortune to have a robust immune system that throws off the infection without much illness.

[escape_velocity]

Maybe "make it lazy" is not the proper way to say it. I mean that by rushing to massacre the invader with outside help you're not allowing the body to develop the antibodies that will stop the next invasion, and so what you're developing is a dependency on outside help, which is not advisable.

 

Forget about the names, then. I'm talking about the small red sores on the inner lining of the mouth that have a light yellowish spot in the middle. I heard them saying on television that they were caused by a herpes virus. It's always only one.

 

Next time I'll put honey through the test because I always have some around, and I do know that it has antibacterial (and antiviral?) properties, but the only alcohol I have is methyl alcohol (industrial alcohol), which is toxic if ingested, because I stopped drinking ethyl alcohol a long time ago, and I'd never go buy vodka just to make an experiment, especially if there's plenty of salt in the cupboard.

 

The quick way salt acts like an anesthetic for external application in this case is surprising, and I wonder whether or not you can expect the same thing if you use alcohol or honey.

 

I'm not being deliberately misleading. I repeat that "in my case most episodes of influenza (or whatever gives you the said symptoms) now last for about half an hour or so". Six decades of frequent battles leave you with an impressive collection of antibodies, especially if you've kept away from antibiotics for one half of that period.

 

Effective home remedies are important now that so many patients are being killed off by "superbugs" that stand up to everything you throw at them. These are superresistant strains and it's happening with diseases like TB that were easily dealt with, which is scary.

 

Pharmacology has to do with chemistry but it now seems like it was a bad idea to bring up the case of the useless lemons. It derailed the discussion. I'd dropped the curtain, but since I was forced to raise it once again I might as well go back to the case of the useless list, and specifically the following two matters.

 

1) Number 10 on the list. The mistake there was relying on an elementary high-school textbook (not Sienko and Plane's, which is the old one and maybe on the junior-college level or higher). That kind of book is proving to be sketchy and simplistic. It says that "the oxidation number is, generally, a periodic property", which on a closer examination turned out to be false, as explained by "mississippichem".

 

2) The problem of n bodies. I wish I knew whether or not the method of the successive or consecutive approximations is ever used in chemistry, so maybe if I describe how it works in astronomy someone will recognize the procedure.

 

The starting point (generally) is today. One calculates for this day all the positions of the planets and all the forces and one obtains the positions and forces for ten days from now, then one reckons them for ten days from that point, and so on. In that way, step by step, one builds the orbit. This requires a huge amount of memory space. That, then, is the numerical approach.

 

With the analytic method one assumes that there's a predominant body, an overwhelming mass, which, in fact, there is --the Sun-- in order to obtain the orbit, then one inputs the forces exerted by the other planets as rectifications to that initial orbit, which is why it's called the method of the disturbances.

 

 

 

 

 

[John Cuthber]

I take it that you are unaware that penicillin (still by far the most widely used antibiotic) doesn't actually kill bacteria.

It stops them reproducing, but it doesn't actually kill them.

So the immune system still has to do that.

Your unevinced assertion about "I mean that by rushing to massacre the invader with outside help you're not allowing the body to develop the antibodies that will stop the next invasion, and so what you're developing is a dependency on outside help, which is not advisable." just doesn't hold water.

 

"I'm not being deliberately misleading. I repeat that "in my case most episodes of influenza (or whatever gives you the said symptoms) now last for about half an hour or so". Six decades of frequent battles leave you with an impressive collection of antibodies, especially if you've kept away from antibiotics for one half of that period."

A couple of points

Firstly, since influenza is caused by a virus the antibiotics can't touch it.

Secondly, have you heard what happens when a bunch of people who will never have met any antibiotics come across a new strain of flu?

It's not pretty

http://en.wikipedia.org/wiki/1918_flu_pandemic

[Anders Hoveland]

All of the following compounds exist:

 

K2FeO4 (brownish-purple color) iron in a +6 oxidation state

Na4FeO6 (green color, unstable, decomposes in sunlight) iron in a +8 oxidation state

RuO4 (ruthenium is directly below iron on the periodic table, ruthenium tetroxide is explosive)

Cs2CuF6 copper in a +4 oxidation state

K3CuF6 copper in a +3 oxidation state

colored complexes containing copper in a +3 oxidation state can be obtained by reacting copper salts with sodium periodate and sodium hypochlorite.

Complexes of Copper in Unstable Oxidation States, T. V. Popova and N. V. Aksenova, Maryi State University, Ioshkar Ola, Russia

 

AgF2 silver in a +2 oxidation state

AgF3 (cannot be prepared by direct combination of the elements) silver in a +3 oxidation state

Au2F10 (exists as a dimer) gold in a +5 oxidation state

NiO2 (commonly referred to as nickel "peroxide") nickel in a +4 oxidation state

XeO4 xenon in a +8 oxidation state

ClF5 chlorine in a +5 oxidation state

ClF6[+] ion (but ClF7 does not exist, since reaction of Cl6+ with F- only makes Cl5 and F2) chlorine in a +7 oxidation state

KO2 potassium superoxide

KO3 potassium ozonide

CsF2 (this is a little researched compound, interestingly it does not seem to be very oxidizing) cesium in the +2 oxidation state,

which is the only +2 oxidation state reported from within the the first column of alkali elements

CsAu gold in a -1 oxidation state

N5[+] pentazenium ion

Edited October 11, 2011 by Anders Hoveland