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Question:
Since atoms are colorless, where do all the colors come from?



Replies:
Materials interact with light in different ways, causing your eye to see different colors. Atoms do absorb light, and so it is not exactly true that atoms are colorless. You would be hard-pressed to 'see' a single atom or its color, but when you group them together, you can see them and their color. As an analogy, it is hard to see a single particle of dust, but when it builds up into dust-bunnies, you sure can see it! Atoms are the same way -- if there is not many of them, they are very hard to see, but when you get enough of them, you can see them.

Although pure elements (an 'element' is a material made of a single type of atom) can have color, the bright vivid colors of nature are usually chemical compounds made of different types of atoms. Chemical bonds -- groups of atoms arranged in just the right way -- will strongly absorb certain wavelengths of light, but not others. Since white light is a mixture of all the colors, if a material absorbs the red and green light, it will appear blue to you. Many famous pigments (like the green color of chlorophyll, the green component in plants), absorb light due to their special arrangements of chemical bonds. Other materials -- colorful minerals like gemstones come to mind -- absorb light due to impurities in their crystal structure (when you substitute a different atom into the crystal instead of the usual one, the crystal will change slightly, and its color will change too). Generally, though, the color you see is due to the material absorbing some of the light, but not all. The light that is not absorbed is the color you see.

Hope this helps,

Burr Zimmerman



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