|MadSci Network: Chemistry|
The color that any material presents to us is based on the manner in which light photons interact with the electrons in the outer orbits of the atoms that conpose the material. In the 3rd edition of the college textbook Advanced Inorganic Chemistry written by Cotton and Wilkinson, on page 65 it is stated that "the properties of metal such as high reflectivity, eletrical conductance, thermal conductance, and mechanical properties are derived from the structural and electronic nature of the metal". The atomic weight of the metal would not be a factor in the color of the metal. The color will depend on the energy level of the electron orbits that interact with the photon of light. If the electron density of the material is high enough the light could be considered to "bounce" off of the atom and the color of the light not changed. If the energy of the light is high enough to interact with the electron shell then depending on the energy of the electron shell a certain color of light will be absorbed and the other colors reflected. When the copper reacts with other elements the electronic structure of the copper is changed and the color (energy) of light that the new compound reflects changes. Oh, remember that the color of a light photon corresponds to it energy. For example, red light is less energetic than blue light. Green light light lies in between. Thats why UV light (ultra-violet, or very very blue light) which is very energetic can cause damage like sunburns to our skin.
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