Which ion is present if an orange-red flame is observed?

• A. Calcium (Ca2+)
• B. Sodium (Na+)
• C. Copper (Cu2+)
• D. Potassium (K+)

Answer: (A)

When metal ions are heated, electrons gain energy and then drop back to lower levels, emitting light at specific wavelengths that act like a color signature for each element. An orange-red flame is characteristic of calcium ions because calcium releases light in the orange-red part of the spectrum when its electrons return to lower energy levels. In contrast, sodium would produce a very bright yellow flame that can overpower other colors, potassium gives a pale lilac flame, and copper shows a blue-green flame. So, seeing an orange-red flame points to calcium ions being present.