Flame emission spectroscopy
|Flame tests can be used to identify some metal ions (cations).|
Lithium, sodium, potassium, calcium and copper compounds produce
distinctive colours in ﬂame tests:
• lithium compounds result in a crimson ﬂame
• sodium compounds result in a yellow ﬂame
• potassium compounds result in a lilac ﬂame
• calcium compounds result in an orange-red ﬂame
• copper compounds result in a green ﬂame.
how to perform a flame test
- Prepare wire loop, beaker of water and burner.
- Heat the wire loop until it glows before dousing it in the water to cool it off. repeat this until the loop does not impart any colour to the flame.
- Use tongs pick up the loop and place your mixture or compound on the loop.
- Insert loop and mixture into the flame and observe the flames colour.
Line spectra are observed when a flame is viewed through a spectroscope. The line spectrum shows discrete lines which are characteristic of the particular element and serve to identify that element.
The image on the left shows the line spectra for some elements.
The image below shows a continuous spectrum.