[mattmckee (OP)]

Hi, some of my pupils asked me what colour atoms were if you could see them, I said good question, I'll get back to you,  so I need some good answers...

Cheers

Matt [?]

[Chemistry4me]

Try this thread: http://www.thenakedscientists.com/forum/index.php?topic=21921.0

It gets a bit off topic somewhere in the middle and at the end. Typical I might add. []

[lyner]

A single atom will absorb a set of single frequencies but would not affect the light going through it much. It would 'look' invisible. This is why we can't see most gases, which consist of many isolated molecules. More dense substances will absorb whole bands of frequencies and somewill then actually appear coloured.

[Soul Surfer]

Colours are usually associated with molecules and multi atomic structures like crystals rather than individual atoms.  this is because individual atoms are around one thousand times smaller than the wavelength of visible light and so they do not interact much with each other.

[Bored chemist]

A lot of coloured molecules are smaller than the wavelength of light and they interact with it just fine.
There are a few coloured atoms, but you don't often see them. Most atoms are pretty reactive. The ones that are not reactive don't have accessible energy levels. If they had they could interact with visible light but they would also be chemically active.