Which of the following ions produces a crimson flame?

The crimson flame is a characteristic result produced by lithium ions (Li⁺) when they are subjected to flame tests. When lithium salts are heated, the energy from the flame excites the electrons in the lithium atoms. Upon returning to their ground state, these electrons release energy in the form of light, manifesting as a distinct crimson red color.

This phenomenon is due to the specific wavelengths of light emitted as electrons transition between energy levels. The unique presence of lithium results in a specific spectrum that is easily recognizable due to its bright red hue, distinguishing it from other metal ions.

Other ions such as sodium, calcium, and barium each produce different flame colors: sodium typically yields a bright yellow flame, calcium gives an orange-red flame, and barium produces a green flame. These varying colors arise from the different energy levels and electron transitions associated with each ion. Therefore, when it comes to identifying which ion produces a crimson flame, lithium is the definitive answer.