Chemical Forums
Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: gregpawin on April 06, 2004, 03:50:04 PM
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Here's a quick little question someone could confirm for me... my professor asked the class today, why is the nitrogen gas molecule so stable? Someone shouted out: because of the triple bond...
Now, that, to me, sounds a lot like a Gchem answer. I recall something about the unpaired electrons in oxygen gas molecular orbitals causing them to be unstable and magnetic of some sort. Would something referencing molecular orbitals or the triple bond answer be more correct?
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I was taught the N=N bond is responsible for rather inert nature of the nitrogen molecule in school too.
Unpaired electron is of course unstable (leads to free radical behavior).
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O=O isnt true? hmm.. is this also how oxygen support combustion as it has contain 2 unpaired electron in e valence shell? WOW!
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Huh radical oxygen held together by one bond? Crazy.
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If you had elemental sodium placed inside a container of elemental nitrogen would there be a reaction. This question points to asking the question how inert is gaseous room temperature nitrogen.
Regards,
Bill
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If you had elemental sodium placed inside a container of elemental nitrogen would there be a reaction
Yes, but less reactive lithium should be used.
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My initial post was merely a hypothetical question for the understanding of reactivity of nitrogen. But after reading jdurg articles on this site about alkali metals, sodium would be the most appropriate metal to do the experiment. Also, abundance also would play a part in the selection. Thank you all for the information provided.
Regards,
Bill
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I repeat the question with a different metal.
If you had elemental iron placed inside a container of elemental nitrogen would there be a reaction. This question points to asking the question how inert is gaseous room temperature nitrogen. My impression is that oxygen will combine with the iron while iron will not combine with nitrogen (over time).
Is that true?
Regards,
Bill
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I can't think of any reactions it would have off the top of my head
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Well if nitrogen is so inert, it shouldn't react with anything, right? Its just chillin... until you do something crazy with it like add a pile of energy.
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Based on the discussion so far, I would say less reactive not inert. Nitrogen is a constituent of ammonia, protein and TNT. It was stated in an above post that nitrogen would combine with sodium at room temperature.
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What I don't get is nitrogen has a full outer shell of electrons, so it shouldn't want to bond with anything, right? I imagine if you pump it full of energy, some electrons will leave the outer orbital, then you'll have some free electrons who want to bond, but I'd imagine you need a lot of energy to send the normal electrons away never to return. So once the nitrogen atom gets its shell full again with the help of another atom, won't the nitrogen want to go its own way again? I can see that as maybe why its good for explosives.
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Full outer electron shell -- I am not sure of that????
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I thought all of the noble gases had that, hence being really inert?
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Nitrogen isn't a noble gas, however. ;D
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Oh crap you're right!!! I feel stupid now. I'm so used to lumping mostly inert stuff in with noble gases ;D
Well since it ain't noble, react away!
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Hold your horses... am I missing something here? I thought that the triple bond was extremely unstable and would cause extreme reactions to occur.
e.g. Ethyne (Acetylene)
How in the world would a triple bond cause stability when it is notorious for being responsible for the extreme reactivity of acetylene? (e.g. Oxyacetylene used in blowtorches ??? )
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Hold your horses... am I missing something here? I thought that the triple bond was extremely unstable and would cause extreme reactions to occur.
e.g. Ethyne (Acetylene)
How in the world would a triple bond cause stability when it is notorious for being responsible for the extreme reactivity of acetylene? (e.g. Oxyacetylene used in blowtorches ??? )
Don't confuse reactivity with thermodynamic stability.
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ok people, there are 3 reasons for the inertness of nitrogen:
1. it is a non polar molecule(unlike CO, with which it is isoelectronic)
2. it has a very high bond energy(triple bond, d uh)
3. according to MO theory, the energy gap between its HOMO and LUMO is very high. the HOMO energy is too low for it to donate electrons, and the LUMO energy is too high for it to accept any.(phew!)
courtesy:
Shriver/Atkins
Cotton/Wilkinson
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ok people, there are 3 reasons for the inertness of nitrogen:
1. it is a non polar molecule(unlike CO, with which it is isoelectronic)
2. it has a very high bond energy(triple bond, d uh)
3. according to MO theory, the energy gap between its HOMO and LUMO is very high. the HOMO energy is too low for it to donate electrons, and the LUMO energy is too high for it to accept any.(phew!)
I hate questions like these because its vague and not necessarily factual in the first place. Although what ksr posted is a good set of predicters it won't always be accuarate for all situations. A simpler answer is that N2 forms few products that will yield an overall negative delta G for some arbitrary chemical reaction.
This assumes we're talking about idealized groundstate singlet Nitrogen. The rules change very swiftly with a bit of energy pumping into the system.
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What about Haber-Bosch synthesis?
The synthesis of ammonia requires very high pressures, high temperatures and lots of iron catalyst.
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Oh yeah, I just remembered. A N2 molecule has all the binding orbitals filled and the non-binding empty
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fwww.av8n.com%2Fphysics%2Fimg48%2Fn2.png&hash=7c4e7ea20438ff7e2929f762a67558cbd23881ae)
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Our air is mostly all nitrogen. Nitrogen in its gaseous state exist diatomically (N2). I haven't heard of any reactions in nature occuring with gasseos nitrogen. I'd imagine for the nitrogen gas to react one of the bonds would have to be broken. Either alot of energy (lightning) or something very reactive (like sodium) will break the bonds. Some bacteria can "fixate" nitrogen. These bacteria are found primarily at the roots of plants to my knowledge. With a catalyst it may react.
From all the posts we can conclude that nitrogen gas is unreactive in nature unless energy is added or it encounters a substance or bacterium capable of breaking one of the bonds.
Anyone have anything to add or was my summary good.
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From all the posts we can conclude that nitrogen gas is unreactive in nature unless energy is added
Yeah, as far as I remember - about 1 MJ per mole to break all three bonds.
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From all the posts we can conclude that nitrogen gas is unreactive in nature unless energy is added
But in some cases is more reactive then oxygen, eg lithium nitride is formed in air in comparable amounts to lithium oxide.
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Lithium though is almost never found as just the element lithium. It is always bonded to something. I said in nature. In nature you don't generally find the alkali metals in their elemental form. That means it is unlikely that a reaction between nitrogen and an alkali is unlikely. In a lab situation you can have what ever you want (with some restrictions).
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In nature, you generally don't tend to find ANYTHING in their elemental form. Nitrogen gets into the ecosystem in some manner, so therefore it has to be reactive.
Lithium is very reactive towards nitrogen. Sodium and the other alkali metals really are not reactive towards nitrogen at all. If you leave some pure sodium metal in a container with nitrogen, you're not going to see any reaction. Replace that sodium with some fresh lithium, and you'll soon see the metal take on a dull coating from the reaction with nitrogen. (This is why pure elemental lithium can be such a pain to work with. It not only corrodes from the presence of oxygen and water, but nitrogen will corrode it as well. For an element collector like myself, this makes lithium a real pain in the ass). ;D
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Nitrogen gets into the ecosystem from large static discharges (lightning) and bacteria that break it down and use it to create other compounds. This is what a biology teacher told me. For it to be of any use to leaving things it must be "fixed". Two ways to do this is what I previously said. There are probably other ways, but I can only think of thoses two.
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Lithium Nitride is rendered highly stable by the fact that anionic and cationic sizes in the lattice are comparable. This is why lithium is the only alkali metal to form a nitride. Both the cation, and the anion are small, and this makes the lattice stable. The other alkali metals are larger in size and cannot form nitrides.
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Monatomic N is an interesting allotrope of nitrogen, it looks like a bright yellow, glowing cloud, and is formed by the action of passing N2 through a corona discharge in a glass tube, with just the smallest trace of O2, larger concentrations of oxygen prevent the formation of N in the monatomic state.
Monatomic nitrogen is metastable, and reverts in time, back to the normal diatomic molecular form.
An interesting fact about monatomic nitrogen is on contact with metallic mercury, it very quickly reacts to form the explosive compound mercury nitride, HgN.
I wonder, if it would react with alkali metal azides, to give a further compound with the formula X-N4, where X is either a transition metal or group I or II metal.
Also, has anyone an insight, or information on the properties of the chalcogen or halogen series' reactivity with monatomic nitrogen? I would be MOST interested to learn more about its properties.
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when magnesium burns in air it also forms magnesium nitride
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ok people, there are 3 reasons for the inertness of nitrogen:
1. it is a non polar molecule(unlike CO, with which it is isoelectronic)
2. it has a very high bond energy(triple bond, d uh)
3. according to MO theory, the energy gap between its HOMO and LUMO is very high. the HOMO energy is too low for it to donate electrons, and the LUMO energy is too high for it to accept any.(phew!)
courtesy:
Shriver/Atkins
Cotton/Wilkinson
could u explain me why the energy difference between homo and lumo have an effect on the reactivity of a molecule especially n2?is that for breaking a bond electrons have to be exited
To a antibonding orbital?please shed light on this .there is also controversy surrounding the m.o. energy level diagram of n2.
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If you had elemental sodium placed inside a container of elemental nitrogen would there be a reaction
Yes, but less reactive lithium should be used.
Actually, and very surprising to many chemists, elemental sodium cannot burn in nitrogen gas, whereas lithium can burn in nitrogen. Despite sodium being considered a more "reactive element", true nitride ions (N-3) are not very stable. It is not favorable for three extra electrons to occupy the smaller outer orbital of a nitrogen atom.
Lithium ions are slightly acidic and can covalently bond to nitrogen. Do some research of the crystal structure of lithium nitride.
One of the reasons why oxygen and nitrogen prefer to exist as diatomic elements is the repelling from the lone pairs.
With only two atoms bonded together, this gives the lone pairs more space. Other elements have few lone pairs, or a biger atomic orbital, which means more space for the lone pairs.