A student investigated an aqueous solution of a salt. The student identified that the salt solution contained only sodium ions and chloride ions.

Describe a test to identify sodium ions. Give the result of the test.

Sodium ions (Na⁺) can be identified using a flame test. This is a qualitative analysis technique. A sample of the compound is introduced to a hot, non-luminous flame, and the colour of the flame is observed. For sodium ions, the flame test produces a characteristic bright yellow or orange colour. This is because the heat from the flame excites the electrons in the sodium ions, causing them to jump to higher energy levels. When they fall back to their original energy levels, they release energy in the form of light of a specific wavelength, which we see as a yellow/orange colour.