Question

Does the emission spectrum produced by burning metal salts in a flame arise from the chloride anion or the metal cation? Design a simple test that would confirm this.

I believe it does and to test it I would burn each component of the compound seperately and compare it to the compound itself ie. for NaCl, I would burn Na, Cl and NaCl separately then compare.

However, could someone find me a credible source and whether my assumption is correct and why? Thanks!

Also, my does hydrogen have a spectrum of red, green and violet when this site: http://www.umop.net/periodic_spectra.png shows us that the visable bands are red and teal?

Answer 1

yes, the emission spectrum produced by burning metal salts in a flame arise from the metal cation this is due to the metal cation can reacquire an electron, becoming a neutral element again. The electron that is gained is in a higher energy level and when it drops to a lower energy level a photon of light is emittted.The wavelength of mostly metal cation is in visible range but most of the nonmetal tends not to emit in a visible spectrum, or their excitation energy is very low. so colour observe from metal salts is only from metal.

The assumption in a test is completely right this is because metal cation Na is electron deficient and tendency to gain a electron and go to higher energy level but at higher energy level they are unstable so emit a photon and drop to lower energy level and the wavelength of emitted photon is in visible range so they produce color.but of Cl anion their exication energy is very low so they can not produce any flame color.

according to rydberg formula hydrogen have a spectrum red (n=3 to n=2) green(n=4 to n=2) violet(n=6 to n=2). but its spectrum is for very small time so if we observe for some time(in second) then we only see that red and teal bands are their. another reason achieving (n=4 and above is very difficult ).