Final answer:
When a cation is burned in a flame, it produces a characteristic color due to the line emission spectra of the metal. Each metal salt has a unique flame color based on the arrangement of electrons. Factors like oxidation states and the presence of water molecules can also influence the flame color.
Step-by-step explanation:
When a cation is burned in a flame, it produces a characteristic color because of the line emission spectra of the metal. The arrangement of electrons in metals determines the unique color produced by each metal salt. For example, the alkali metals produce different colors such as yellow for sodium, bright crimson for lithium, and pale violet for the others. Additionally, changes in oxidation states and the presence of water molecules around the metal ion can also impact the flame color.