[kevinnn]

The stars in fireworks are what produce the display we all like. My question is, for example strontium, which of course makes most of the reds in fireworks, when the red is produced it's because of the electrons moving from an excited site to their ground state. I get that. But when I quickly thought more about it I wondered about it on a more fundamental scale.  In the process of producing the light  does it form strontium oxide and strontium nitride which is what i would predict or just what does it do?  When the red is being produced what is everything that is happening to the strontium atoms.
Thanks. 

[Arkcon]

The thermal excitation of the solid strontium containing salt does also cause it to undergo side reactions yes.  You seem to almost realize that these side reactions don't affect the electron transitions associated with the light emission.  If you're wondering what happens after the light, can you guess, based on where the star composition is, at the point when you see the color?

[kevinnn]

  I have never actually thought about it. I'm not actually too sure. If I had to guess I would say that it falls to the ground as new strontium compounds.  But since you said the reactions were side reactions that can't be the whole picture. So I have to assume that most of it falls back to earth as strontium in the ground state but in smaller chunks than that of the original star because the heat and side reactions would help break it up. Is that going down the right track?   

[Arkcon]

What have we got, on the surface of the planet Earth ... and in the, erm, atmosphere that would likely form a compound with a glowing red hot particle of an alkali metal? 

[kevinnn]

It is water? 

[Arkcon]

I suppose that's not impossible.  But the oxides of alkali and alkaline earth metals are considered refractory materials. http://en.wikipedia.org/wiki/Refractory They are so oxidized, they can't react with anything further, and make good crucibles for melting metals and other high temperature reactions.  So I think its fair to say that that is the final resting place, as it were, of those active metals.  Especially if you're spraying them into the air as a red hot dust.

[kevinkevin]

  So the final result of the star is just a stable oxide of the metal?   

[billnotgatez]

http://en.wikipedia.org/wiki/Atmosphere_of_Earth
http://en.wikipedia.org/wiki/Nitrogen
http://en.wikipedia.org/wiki/Oxygen
http://en.wikipedia.org/wiki/Strontium

Strontium is a grey, silvery metal that is softer than calcium and even more reactive toward water, with which it reacts on contact to produce strontium hydroxide and hydrogen gas. It burns in air to produce both strontium oxide and strontium nitride, but since it does not react with nitrogen below 380 °C, at room temperature it will only form the oxide spontaneously.

Based on the above links, it is a good bet that strontium oxide is the only result produced.
Oxygen and Strontium are reactive and Nitrogen is relatively inert.
The question is "Does the activity of fireworks sufficient to do the non-spontaneous".

[kevinnn]

  From what it looks like, yes. The stars of fireworks do burn hot enought to do the non-spontaneous reactions. Is the importance of that question.  For us to know that strontium nitride will be produced? 

[billnotgatez]

Thinking about this more it is not elemental  strontium that is reacted. It is typically the carbonate of that element.

[kevinnn]

  Yes of course. Sorry that was stopid on my part. Everywhere I said strontium atoms I meant to say strontium ions.
  When I make stars I use strontium chloride. I never thought to use strontium carbonate. Would that be harder to get a hold of you think? Strontium chloride is so easy because I use it for one of my other hobbies, marine aquarium. Strontium chloride is used as a supplement to replenish strontium ions in the aquarium. 

  Back to what you said though billnotgatez, does that affect the question you asked me earlier.  Or did I answer the question? 

[Arkcon]

You choice of anion when building your star depends on how you've designed your formulation.  Carbonates and oxides are used to make a star (or say, fountain composition) less brisant, to slow down a reaction that's going to fast for people to see it.  On the other hand, the composition needs some oxidizer, and sometimes the colored salt is used to help, for example, bursting charge can be made with barium nitrate or barium chlorate, that's what gives flash powder its flash.

[kevinnn]

Thanks for that. Very interesting. I would have thought that a chloride contaning salt would have made the display less brisant because the compound would then contain no oxygen. With the carbonate ions or if it were an oxide I would have thought that it would accelerated the reaction because the molecule itself would now contain oxygen. 

[Arkcon]

Its a funny thing to understand what is more or less brisant, based only on the atoms it contains -- for example, perchlorates are less brisant than chlorates, even with one more oxygen atom.  This sort of information is well contained in books on pyrotechnics, the canonical sources are books by Weingart (an older author) and Lancaster (a more modern author -- an Anglican minister known as Master Blaster Pastor.)  George Plimpton wrote a very easy book on the history of fireworks that touched on some of the knowldge and how it was learned.
http://www.amazon.com/Fireworks-History-Celebration-George-Plimpton/dp/0385154143

[kevinnn]

  Since this is now the secod time I have heard the title of this book brought up it may be worth buying. Thanks for the link.
  My only remaning question is the one you guys brought up earlier. You keept asking me to answer what happened after the star was exausted and the red light died as the star fell back to earth. Did I answer that question?