Which compound forms a colored aqueous solution?

Question

a) CaCl2 c) NaOH
b) CrCl3 d) KBr

i think its Cr because its an transition metal. but im not sure.

Answer 1

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.