Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: ChemKid on May 01, 2005, 10:22:31 PM
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Hi, I cant't find the answer anywhere. Why doesn't helium burn?
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Helium is extremely unreactive, it is one of the noble gases, the ONLY reactions other than simple state-changes helium has been made to undergo are nuclear transformations, which do not follow the usual chemical laws.
In short, there is nothing known that helium will react with, combustion requires an oxidation reaction of some sort, which involves the fuel reacting and combining with another element, such as oxygen, or a halogen, helium doesn't undergo these sort of reactions (under conditions that we know of) and hence, will not burn under any circumstances.
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Put extremely simple.
Helium has all 8 of its valence electrons (outermost electrons).
Oh really? ::)
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Put extremely simple.
Helium has all 8 of its valence electrons (outermost electrons). That leaves no space for any other electron which makes it extremely stable. Remember things only react/burn when it is forming a more stable substance. What is more stable than have a full outer shell? Nothing.
That is why helium and the other halogens do not burn.
As limpetchicken stated the only helium's radioactive isotopes change because anything radioactive is not stable. Also when you fuse helium molecules or if you split them will it "burn" although it is not burning it is just releasing tremendous amounts of thermal energy.
I think you have a case of cerebral flatulence there thinker. ;) ;D Helium does have a full shell of valence electrons, but that full shell is comprised of 2 electrons and not 8.
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By golly your right! I guess I wasn't paying attention because most elements are full at 8 unless they go to the next lowest level. My mistake :)
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Check out some of the stuff that Gerber has been calculating. His group and another in the netherlands have synthesized the first argon compound, HArF. They calculated that HHeF is stable at about 2.5K and 15GPa of pressure. Personally, I think a lot of those calculations are a load of crap, but they did managed to synthesize HXeCCH, HKrCCH, HXeCN and HKrCN, and that crazy argon compound, so who knows?
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That is why helium and the other halogens do not burn.
I thought that Chlorhine, Flourine, Bromine etc. were the halogens and Helium, Neon, Krypton etc. were just called "noble" or "inert"
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Many simple charged Argon compounds have also been known for quite some time. ArH+ to name just one.
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Wow I'm starting to realize that my earlier post is fraught with errors. Very, very dumb ones and I know better. My apoligies. I will delete it.
Helium has all its valence electrons. Which is 2 in this case. Things only react to form a more stable substance. There isn't anything more stable than a complete outershell. That is why the noble gasses do not burn.
As for the synthesising with helium I've never heard of any sythesis with the inert gasses. I'll take your word for it though.
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Things only react to form a more stable substance.
That is incorrect. Also, please never use the word stable again.
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Mind me asking but how is that incorrect. I would like to understand and learn. From my knowledge (and I'm still in high school. I'm a sophmore) things react primarily to form a substance that doesn't have any spots for electrons. This is atleast from my knowledge which includes an A in level 4 physical science and talks with a chemistry teacher. Maybe I'm not seeing a bigger picture or I've forgotten alot in a year.
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things react primarily to form a substance that doesn't have any spots for electrons.
I usually answer questions with more questions, so please excuse my next question for you.
Can you name any reactants that are "missing spots" for electrons? So, this is what I need you to do, and what you must do in order to learn. Please post a chemical reaction that shows a reactant having "empty spots" for electrons.
I will not answer why you are banned from using the word stable, please do a forum search for previous discussions on the matter
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Ok, I will do that tommorow it is getting late on the east coast.
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Yeah, but in what form were the argon species? Excited states. This is a ground state argon compound. Pretty cool.
As for the question about stability, you need to remember that we're dealing with professors who will own you for saying something about 'stability'. Thinking about it in terms of stability is probably perfectly fine through HS and even most of college. The problem comes when someone asks you 'What's more stable?' If you think about it, it's really that the compound is more reactive. Then you get back into the electron count, etc. However, there are also compounds that are thermodynamically unfavorable, but can still be made. It just depends on how much energy you can put in and in what manner. Take a look at cubane. Thermodynamically, it is extremely unfavorable (you've got to put a lot of work into making it). Kinetically, it's solid as a rock. This is how many of these noble gas compounds are made: although it is thermodynamically unfavored, they add the necessary energy by blasting it with UV light or fast electrons, and then new molecules form, which have a kinetic barrier to dissociation.
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It was an excited state of Argon.