It's been bugging me for a long time that alkali metals explode. That shouldn't happen in a heterogeneous reaction.
In trying to work this out, its become more and more intreging!
The metal explodes at near speed of sound (detonation). But even more interesting, it gives off green gas, up to the point the metal is incandescent (~600C).
Still not sure what causes the explosion. Standing waves on the molten surface? The metal boiling. Nothing quite fits.
The green gas however it turns out has been known for a LONG time, well over a hundred years as being related to potassium vapor. Ask the question why is it green, and I've drawn a blank. Can't find anything.
Modern research has done quite a lot with dipotassium (electronically similar to hydrogen), but these are not the brute experiments of old of heating tubes up to red heat and eyeballing it.
I suspect, but don't know that the green gas is dipotassium. It's electronic configuration is similar to that of chlorine. Chlorine is green due to the raleigh scattering (same thing that makes the sky blue). If the polarization of Cl2 and K2 was similar, the colors would be similar. That would of course put Na2 being a much lighter green. It's not, its blue.
So what are the alternatives? Solvated electron would be a credible explanation for the current water case, but according to the ancient literature, you get the same vapor when you distill potassium.
ARSE! Still there are a lot of eyes and minds out there! Hopefully one of them will spot the obvious that I am missing.
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