A flame test uses which type of flame?

• A. Non-luminous
• B. Luminous
• C. Neon
• D. Green

Answer: (A)

A flame test relies on seeing the colors produced by metal ions when they are heated. To observe these colors clearly, you use a non-luminous flame—blue, clean, and hot—because it comes from complete combustion with very little soot. That means there’s minimal background yellow light from incandescence, so the bright, characteristic colors of the metal ions aren’t masked. If the flame were luminous, soot would glow yellow and interfere with or hide the ion colors, making identification unreliable. Neon would introduce its own color from the gas, not from the metal ion, and green describes a possible observed color but not the type of flame. So, the non-luminous flame is used.