All matter is made of atoms. Atoms have a nucleus, consisting of protons and neutrons, surrounded by electrons. The nucleus is concentrated in a very small space, about 10−15 m. An entire atom is on the order of 10−10 m, so the electrons are relatively far from the nucleus, and, strangely enough, atoms are mostly empty space.
Physicists have found that the electrons traveling around the atomic nucleus can have only certain specified energy levels. In other words, the energy levels of atomic electrons are quantized. When provided with more energy, the electrons can move from one energy level to another, but these different energy levels are not continuous—they come in discrete steps. This fundamental discovery is known as quantum mechanics. Quantum mechanics describes how an atom's electrons interact with electrons of other atoms and with photons.
Atomic electrons at higher energy levels can also lose energy, dropping down to a lower energy level. Again, the electron moves from one allowed energy state to another. The lost energy can be carried away in the form of heat (vibrational energy) or in the form of light—when the electron reverts to a lower energy state, a photon of light is produced. The photon produced will have an energy equal to the difference between the electron's initial high energy state and the later lower-energy state. For visible light, we perceive these differences in photon energy as differences in the color of the light.
In this project, we will use a procedure that is similar to flame photometry to observe the color of light produced when various chemical compounds are burned. The experiment have to be performed carefully so that the flames stay small and under control.
Rainbow Fire. (2013, March 22). Retrieved July 10, 2013, from http://www.sciencebuddies.org/science-fair-projects/project_ideas/Phys_p058.shtml