What color flame does copper ii gluconate produce

The color flame is green.Because the metal cation in the molecule tends to release energy in the form of visible light.

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I would expect copper (II) gluconate to produce a green flame. This is because the metal cation in the molecule tends to release energy in the form of visible light. Many potassium compounds, when heated in a flame, emit purple light, while many copper compounds emit green light.

Answer is to avoid experimental error