Colors of Elements in a Flame - Animation of Photon Emission

Photon emission is illustrated using an animation.

The animation is highly schematic. It shows a set of energy levels for a hydrogen-like (one-electron) atom or ion. Collisions of an atom with other fast-moving atoms in the flame can raise an atom to an excited state, after which the atom can lose energy by emitting a photon. The color (wavelength) of the photon depends on the energy difference between the upper and lower energy levels.


Aqueous solutions of various compounds are sprayed into a Meeker burner flame from an atomizer. The flame colors are demonstrated close up. Except for boric acid, all compounds are chlorides. Aluminum chloride or magnesium chloride can be used to demonstrate that chlorine imparts no color to the flame.

These movies are 3 to 5 seconds in length. There is no sound or voice over.

Metal salts introduced into a flame give off light characteristic of the metal. Metal ions combine with electrons in the flame and the metal atoms are raised to excited states because of the high flame temperature. Upon returning to the ground state, they give off light (a line spectrum) characteristic of that metal.

Several metal salts give off a characteristic color visible to the human eye as is demonstrated by the alkali metals and a few other elements, but a fair number of metal salts give off light that may be observed, but is not sufficiently different in color to be differentiated from other metal salts. Some metal salts give off light outside of the visible region of the electromagnetic spectrum.

In these video sequences selected compounds, mostly metal salts, show the flame color in a Meeker burner flame. A homemade atomizer was used to form a fine spray of the solution, which was sprayed directly into the burner flame.

It should be noted that sodium is present as an impurity in many if not most metal salts. Because sodium imparts an especially intense color to a flame, flashes of the sodium may be observed in nearly all solutions tested.

  • Design and Animation
    • Jerrold J. Jacobsen University of Wisconsin - Madison, Madison, WI 53706