A little more on flame tests.
Copper is one of the easiest to identify in a flame test and in many cases is THE diagnostic test..
When doing a flame test ensure the sample is not placed in the blue part of the gas flame. The blue part of a gas flame is caused by oxidising methane and could confuse the colour signature. Where the blue finishes and the flame turns near or completely colourless is where the methane has completely burnt, is the hottest part of the flame and where the sample should be placed.
The thermal energy of the flame excites the copper ions and this energy is released as the copper ions cool down as they move to cooler parts of the flame. This energy is released in discreet packets as photons of different wavelengths representing different colours. Quantum mechanics in operation.
Unfortunately gold is not one of the elements that can be easily identified by this method as the energy levels required for ionising and exciting gold atoms would be far in excess of the hottest flame available to us. XRF type machines however can do this by using high energy X rays.
