Account for the following :
(i) `PCl_(5)` can act as an oxidising agent but not as a reducing agent.
(ii) Halogens are coloured.

Explanation

(i) `PCl_(5)` can act as an oxidising agent but not as reducing agent : Oxidation states shown by phosphorus is `+3 and +5`. Its valence shell has 5 electrons. Hence it can oxidise others and itself gets reduced by accepting electrons and get converted into `PCl_(3)`, but cannot show more than `+5` oxidation state.
(ii) Halogens are coloured : The colour of halogen is due to absorption of visible light by their molecules resulting in the excitation of outer electron to higher energy levels. e.g., Fluorine being smaller in size abosrbs violet light and appears pale yellow.