# Increasing Covalent character increases Colour intensity

I observed some trends as follows:-

• $\ce{PbCl2}$ white and $\ce{PbI2}$ yellow
• $\ce{SnCl2}$ white, $\ce{SnCl4}$ red and $\ce{SnI4}$ black
• $\ce{AgCl}$ white, $\ce{AgI}$, $\ce{AgBr}$ and $\ce{Ag2CO3}$ yellow

In all these cases as the size of anion increases ( polarisability increases) or charge on cation increases (polarising power increases) colour exhibited becomes darker.. How does increasing covalent character affect this? Or is there any other reason?

• In silver compounds colour is mostly due to charge transfer. – G-man Jan 23 '16 at 12:17
• tin(IV) chloride is a colorless liquid and tin(IV) iodide is orange solid. – Nilay Ghosh May 7 '16 at 3:48