Ask A Scientist Chemistry Archive

Question:  Do you know why crystals are different colors depending on what
chemical you use?  We couldn't find any answers in the encyclopedia.
 eileenb

Answer:
Depends on the type of bond that's in the crystal.  Copper nitrate crystals
are blue because the Cu-N bond absorbs orange (?) or whatever is blue's
complimentary color and reflects blue.  Potassium dichromate is a brilliant
orange for the opposite reason.  Check the chem archives too for
a solutions colors discussion.  I seem to remember something like that
a while ago.
-Joe Schultz