What does nitrogen in air do for us?
Nothing. The world isn’t meant for us; it just is.
But if you absolutely need some sort of positive effect, it marginally lowers the risk of explosions by lowering the percentage of oxygen, I guess.
N[sub]2[/sub] is better known for what it doesn’t do, namely participate in many chemical reactions. That inertness is the reason why nitrogen released in tiny amounts from volcanic activity has had a chance to build up a sizable presence over the millennia, so that it now accounts for about 78% of the atmosphere.
Say it with more bitterness: “what the hell did nitrogen ever do for US?”
As it turns out, it’s pretty useful:
without it, plants and animals would not be what they are.
it’s also useful for slowing down fires. Even if the partial pressure of O2 in the atmosphere remained at ~3 psi, the removal of nitrogen would remove a crucial heat sink/diluent: fires would burn much hotter and faster than they do now, and internal combustion engines would probably detonate (knock) severely. Whereas normal wildfires tend to smolder and eat up the latest bit of undergrowth, wildfires in a pure-O2 atmosphere would burn much hotter, faster, farther, and more completely than they do now. Instead of clearing the forest floor for new undergrowth, they would incinerate forests from the treetops down into the soil, making forest biomes start over from scratch on a regular basis.
What makes you think it’s there for us?
[Dr. Frankenfurter: “I didn’t make him for you!”]
We exist in a world with plentiful nitrogen. We’ve evolved with it as a circumstance. It’s essential for an awful lot of the life chemistry that goes on. Our most obvious dependence on it is in using it (in chemically combined form) as fertilizer for plants. we eat the plants or the animals that feed on it.
It shows up in that cycle because it’s essential to making amino acids and proteins. It’s part of DNA and RNA.
But it might not seem as obvious a need, because if you shut off our access to nitrogen we don’t immediastely die, as when you cut off access to oxygen.
Myself, I always thought nitrogen was there to give us a convenient cryogenic fluid. Using liquid oxygen to cool things results in heightened danger of flame and explosion. Most other things you can use are dangerous or rare. Carbon dioxide form a solid, not a liquid. But liquid nitrogen gives you a nice, stable 77 Kelvin and evaporates away with no ill effects (unless you displace too much oxygen in your room), and the best is the air is already 3/4 nitrogen!
nitrogen in the atmosphere gets cycled and fixated and oxidized.
Aside from being not terribly chemically reactive, it is also mostly transparent to infrared, visible, and near visible ultraviolet light, but absorbs more in the high frequency ultraviolet region, making it an excellent medium to support photosynthetic life.
This is true, although the fixing of atmospheric nitrogen into biologically useful nitrates is done mostly by bacteria and a few classes of plants. Nitrates are critical for both providing nitrogen (which provides the nitrogenous base for amino acids and glues together nucleotide sequences to form complex nucleic acids) and delivering other biologically critical metals and metallic compounds formed form phosphorous, potassium, calcium, and magnesium. Although life (our type of life, at least) is typically referred to as “carbon-based”, nitrogen is equally critical to all life as we know it, and we’d be hard done by without a readily accessible source of nitrogen.
Nitrogen is also one of the deadliest gases in industrial use. Because there is not smell, flavor, or color, it can’t be readily identified, and in the respiratory system it acts as a substitude for diatomic oxygen, and because of the molecular weight it tends to sink and collect in low or enclosed areas. It is therefore possible to asphyxiate in an atmosphere of high concentration nitrogen without ever realizing it, and therefore should be treated as a dangerous substance in any significant quantity.
Stranger
Just to make it crystal clear: a lot of biochemistry relies on molecules that contain nitrogen atoms. DNA and proteins spring rather quickly to mind. However, the atmosphere contains molecular nitrogen, N2, which is a ludicrously stable molecule. We humans can’t do squat with it directly. Until recently (when someone invented a way to fix nitrogen in the lab), all life on Earth, including us, relied on the ability of a few kinds of microbes to take atmospheric nitrogen and turn it into something useful for the rest of us.
Nitrogen is actually slightly lighter than air, but still can easily asphyxiate when released in large quantities or in confined areas.
plus nitrogen is capable of some loud and entertaining things when you try to cram too much of it into a molecule.
I remember some of those compounds - Corrente (sp) had/has a humorous blog about chemicals he won’t work with in the lab. I think another lab put togther a titanium atom with 12 Ns lasting a few minutes. N really, really like to be N2.
It doesn’t do anything. That’s the beauty of it!
Most of the nitrogen in biological systems isn’t in the form of nitrates, it’s in the form of ammonium, amide or amino groups (or in some cases, as in nucleic acids, incorporated within rings). Nitrates are an oxidized form of nitrogen: those other species are reduced forms (i.e. bonded to things with lower electronegativity, like hydrogen or carbonm).
Also, phosphorus isn’t a metal, and I don’t think nitrogen ‘serves as a substitute’ for oxygen (if by that you mean reacts with molecules that oxygen would otherwise react with). It doesn’t easily react, that’s the point.
yeah, that’s Derek Lowe’s blog as Chronos linked to. Nitrogen really really really really wants to be a gas, and will do a lot of loud and amusing things to get to that state.
Hmm… what movie was that from?
That’s the stuff they use to inflate your car’s airbags right? Azides.
Derek also doesn’t like Fluorine.
What does fluorine do for us? (Besides making our teeth not rot.)
It’s nice to have this dense atmosphere without it being all highly reactive. It allows birds to fly and meteors to burn up before hitting the ground.
A TV show, “Burke’s Law”. Mystery quote: ''It doesn't do anything. That's the beauty of it.'' - Cafe Society - Straight Dope Message Board
Good Lord, nothing about the Haber Process?
Condensed summary:
Plants (as well all other types of life on earth) need nitrogen as part of the simple building blocks of life
There is a large amount of nitrogen in the Earth’s atmosphere - but most of it is inaccessible as it is in the form of N2, nitrogen gas, which is mostly inert and difficult to get to do anything. With slow crop rotation and nitrogen-fixing bacteria: soil will slowly take up nitrogen, but this is not nearly fast enough to support the current human population.
Haber figured out an industrial process to take nitrogen gas from the air, and under pressure and heat with catalysts make ammonia. So what? From ammonia, rather than inert N2, you can make nitrogen-based fertilizer pretty easily. “Bread from air”. That was the slogan at the time, and it’s honestly not too far from the truth.
…it also, unfortunately, led to development of some pretty powerful explosives. So Haber’s legacy isn’t perfect.
But per Wikipedia: “Fertilizer generated from ammonia produced by the Haber process is estimated to be responsible for sustaining one-third of the Earth’s population.”
That’s a pretty significant effect of nitrogen.