Which metal ions produce distinctive colours in flame tests?

The presence of specific metal ions in a sample can be identified using flame tests, which produce characteristic colors when the sample is heated in a flame. In the case of lithium, sodium, and potassium, each ion emits a distinctive color due to the excitation of electrons in the metal ions.

Lithium produces a crimson red flame, sodium emits a bright yellow flame, and potassium results in a lilac or light purple flame. These colors are a direct result of the energy released as the excited electrons return to their ground state, which corresponds with the wavelengths of visible light emitted.

The other options do not consist of metal ions known for producing recognizable flame colors. While aluminium, calcium, magnesium, iron, lead, zinc, copper, silver, and gold have various applications and properties, they either do not produce visible colors in a simple flame test or have less distinctive colors that may not be easily identified without more complex procedures. Thus, lithium, sodium, and potassium are the primary ions used for straightforward identification through flame tests in a laboratory setting.