I can't even begin to list all the things confusing (or perhaps totally wrong) about the Dept. of Energy's answer:<p>> <i>atoms do not have colors</i><p>Then why do group of atoms (eg. gold) have a color, but not an individual atom?<p>> <i>If the electrons give out exactly the same light as they absorb, the substance is "colorless"</i><p>Shouldn't the answer be "white" rather than "colorless"? Colorless sounds like transparent or clear to me.<p>He uses absorb, reflect, and emit inconsistently. Surely, there has to be a clearer explanation somewhere on the Internet?
Interesting, my first thought jumped to gold and the 5d->6s transition that is well-known for needing relativistic consideration to correctly predict the yellow color.<p>I don't think the answer given is a great one, but I like that they sent a correction.