posted by John on .
Which compound forms a colored aqueous solution?
a) CaCl2 c) NaOH
b) CrCl3 d) KBr
i think its Cr because its an transition metal. but im not sure.
It is Cr and the reason is that it has unpaired electrons. The electron configuration for the neutral element is
1s2 2s2 2p6 3s2 2p6 3d5 4s1 and when you mak the 3+ ion (as in CrCl3), you take off the last three electrons to give you
[Ar]3d3. Remember the d orbital has five lobes
_ _ _ _ _
x x x
The x stands for an electrons. In fact, almost any way you slice it, Cr has unpaired electrons for almost everything.