Question: when you burn magnesium why does its burn really brightly?

Ed Lowe answered on 17 Jun 2013:

I’m afraid we have to think about atoms and electrons for this! When a metal burns, what is happening is that the metal is reacting with the oxygen in the air which will produce a metal oxide and also some energy. This energy is what produces the light, indirectly. The energy will cause electrons in the metal to jump up into a higher energy shell – this will generally be unstable, so the electron will drop back down to its stable state and give the energy back out again as light (we tend to refer to that light as a photon with a specific energy). The gap between these states will determine what colour the light is (it is different for different metals) and in the case of magnesium it is right up at the UV end of the spectrum.
Incidentally, if you ever actually try doing this make sure you don’t look directly at the magnesium, the light is easily bright enough to damage your eyes.