The Colourful Compounds of Copper

Diana O'Carroll

Why are copper compounds so colourful?  In this week's Question of the Week we find out how one metal can have so many colourful compounds, as well as a distinctive green flame.  Plus, we ask why dreams are so hard to remember, even the really good ones, and how can a frog can breathe through its skin, with no help from lungs or gills?