The mechanism of color generation of conductor metal materials
Of the metals that make up about four-fifths of the elements in nature, with the exception of a few, such as gold, copper, and bismuth, which are golden yellow, all are silvery or off-white shiny opaque solids (mercury is a liquid). This is due to the nature of all substance is a dynamic balance of the body, the metal is made up of a metallic bonding in combination with metal crystal, just inside the metal free electrons or resonant frequency corresponding to the specific frequency band of visible light, so easy to absorb the visible light of a specific frequency band energy transition, arrived at the higher level, in a state of flux, then spontaneous transition back to the original level, then to external radiation in the form of light.But most metal free electrons absorb all wavelengths (frequencies) of visible light and then reflect them back almost entirely, so most metals are silver-white or off-white. However, a few metals absorb a certain wavelength of light in visible light to a greater extent, and other wavelengths of light to a lesser extent, so the metal takes on a specific color. In copper, for example, the conduction band is only half full. The empty energy level is adjacent to the filled energy level. Electrons absorb visible light easily. It can be known from the flame color reaction that they mainly absorb green light. When all metals are in the powder state, the crystal face of the metal is very messy and the crystal lattice is arranged irregularly. All the absorbed visible light cannot be radiated out. Therefore, most metals are black in the powder state.
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