flame test(F.6)

你的問題很好，帶出 flame test 發光，是不同於化學反應(reaction) 時的發光。

化學反應(reaction) 時的發光現象，是 specific observation...每個反應有不一樣的 observation。有的反應發熱，有的發光．

Flame test 發光，正如你理解，是 electron 在不同 quantized level of orbital 停留時，把energy 以 photon 方式發射出。（Eject uncharged photon from electronic fields made of molecular orbital and electron) 當中 electron spin 帶出 fine structure, 如 soudium D line etc. (reference 2)

發光的化學反應，不是一個 Mg atom 帶出的。所以，白光是 continuous spectrum，不象 emission spectrum 有 specific wavelength。
也因 Mg + oxygen --> MgO 的化學反應是 continuous spectrum，白光可以用於 photography (giving most reliable colour temperature in flash photography)

Dr Lam

reference 1) difference between flame test and oxidation of Mg by burning

http://www.newton.dep.anl.gov/askasci/chem03/chem03362.htm

reference 2) emission spectrum of Mg by gas discharge

http://astro.u-strasbg.fr/~koppen/discharge/magnesium.html

2008-08-17 14:58:57 補充：
2Mg + O2 --> 2MgO (give out 白光) Electron DO NOT jump back to Mg orbital! It is a oxidation reaction!!! Electron goes from Mg to O! Mg become Mg2+ (no s electrons anymore); O become O2-

2008-08-17 14:59:07 補充：
Mg/Mg2+ burn in flame --> give out emission spectrum, just like reference 2. No 白光 give out. Flame test, electron is from the flame! Electron sits and jump between different quantized orbital of Mg, and the energy difference is emitted as photon. There is no redox in flame test.

2008-08-17 14:59:11 補充：
White light is continuous spectrum.... atomic emission have quantized levels, ie just give out line spectrum.