We can think of the collection of characteristic phtons emitted by each chemical element as a kind of fingerprint because each of these collections will be consist of a set of wavelengths that is distinctive for that chemical element only. By definition, the total collection of photons emitted by a given atom is called its spectrum, a characteristic pattern that can be used to identify chemical elements even when they are very difficult to identify by any other means. This method works because light from gaseous atoms is spread out after being passed through a prism. Each possile quantum jump corresponds to light at a specific wavelength, so each type of atom produces a different set of lines.