Elements emit colours when heated because electrons in atoms can have only certain allowed energies.Heating an atom excites its electrons and they jump to higher energy levels. When the electrons return to lower energy levels, they emit energy in the form of light. Every element has a different number of electrons and a different set of energy levels. Thus, each element emits its own set of colours. See, for example, mercury and neon above. Those colours are as distinctive to each element as fingerprints are to people.
The economic cost to society each year from crashes and injuries on U.S. highways is <u>242 billion dollars</u>. Approximately, this may be about $784 per crash.
