Why does the color of the halogens deepens as we go down the group? also why there is a change in physical state of halogens down the group?
\begin{array}{c|c} \mathbf{Gas} & \mathbf{Color} \\\hline \text{fluorine} & \text{very pale yellow (almost invisible to naked eye)}\\ \text{chlorine} & \text{yellow-green} \\ \text{bromine} & \text{red-brown}\\ \text{iodine} & \text{violet-black}\end{array}