Why is bromine a weaker oxidizing agent than chlorine?

Bromine is a less powerful oxidizing agent than chlorine primarily because the bromide ion undergoes weaker hydration compared to the chloride ion.1

While both elements possess high electron affinities, the overall oxidizing strength of the halogens is influenced by several factors, including the energy required to dissociate the diatomic molecules and the stability of the resulting ions in solution. The weaker hydration of the bromide ion relative to the chloride ion contributes to bromine's reduced ability to act as an oxidizing agent in aqueous environments. Additionally, the chemical reactivity of bromine is generally intermediate between that of chlorine and iodine, reflecting these underlying differences in ionic and bond stability.12