I have a torch lighter and it makes a green color when the flame passes over the metal in the center. What on the molecular level would a flame change color although there is no difference in temperature? Do some elements produce a different color when exited?
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@JohnRennie The concentration of metal ions has an obvious effect as the more metal ions there are the more light will be emitted. There isn't a direct connection to the colour.– John Rennie – Muze Apr 27 '16 at 14:44
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I want to know the direct connection to the colour. – Muze Apr 27 '16 at 14:45
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1It's directly related to electron configuration. Especially the valence electrons. Every Element has a unique arrangement of electrons and when they get excited they jump back-and-forth between different and unique energy levels. – Bill Alsept Apr 27 '16 at 14:50
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This is one of the first examples of energy levels for electrons within the atom!
If we take the Bohr model, which imagines that electrons circle the nucleus on set orbits
Each of these orbits has a corresponding energy. The electrons are more stable at lower energy levels, and thus, prefer to be there.
When you provide energy to the electrons (in the form of the flame/heat energy) they get excited and jump to a higher energy level.
Unfortunately, at the higher energy level, the electrons are unstable and will eventually fall to the lower energy level. When this happens, the energy which they absorbed has to be gotten rid of in some way. This means that the electrons eject a photon of energy equal to the energy difference between the two levels.
Different energy photons have different wavelengths/frequencies, which are associated to the colours which they are. Higher energy waves are more purplish, (until they enter into ultraviolet and can't be seen by the naked eye) and lower energy waves are red (until you get low enough energy to enter into the infrared region).
The flame's colour changes due to the difference in the energy levels. Elements have set energy levels, so the only way you can get different colours is by using a different element in the flame, or by exciting the electrons to even higher energy levels. Unfortunately, the latter option is not really possible for you. Most of the electrons will be just jumping up to the second energy level, whereas very few would be jumping higher, meaning that any different coloured photons will not be visible amongst the rest.
A few examples of these elements and colours are: Copper - blue-green, Potassium - lilac, Strongtium - red, Sodium - yellow (like sodium street lamps!), Lithium - dark red, Barium - green.
Figure taken from Wikipedia's article on the Bohr Model.
