Q.Why halogens act as oxidising agents?

Step 1. An oxidising agent is a species that gains electrons (and is itself reduced) in a redox reaction -- so a strong oxidising agent must itself have a strong tendency to accept an electron.

Step 2. Halogens have the general configuration $ns^2 np^5$, just one electron short of the stable, completely filled $ns^2 np^6$ noble-gas configuration.

Step 3. This makes halogens the elements with the highest electron gain enthalpy magnitude in every period (Section 3.5.4) -- they very readily pull an extra electron from another species to complete their own octet. …

Connect the definition of an oxidising agent (electron acceptor) directly to the halogens' high el …

• Explaining halogen reactivity in terms of electronegativity alone without tying it explicitly to the redox defin …