Why is chlorine a stronger oxidising agent than iodine?

Chlorine is a stronger oxidising agent than iodine because it has a higher electronegativity and a stronger ability to attract electrons.

In the context of redox reactions, an oxidising agent is a substance that has the ability to oxidise other substances, meaning it can gain electrons from other substances. The strength of an oxidising agent is determined by its ability to attract and accept electrons. The more electronegative an element is, the stronger its ability to attract electrons, and thus the stronger its oxidising power.

Chlorine (Cl) and iodine (I) are both halogens, found in Group 17 of the periodic table. They have seven valence electrons and need one more electron to achieve a stable, full outer electron shell. This makes them naturally inclined to gain electrons, hence their role as oxidising agents. However, chlorine has a higher electronegativity than iodine, meaning it has a stronger ability to attract electrons. This is due to its smaller atomic radius, which allows the positively charged nucleus to exert a stronger pull on the electrons.

Furthermore, the standard electrode potential of chlorine is higher than that of iodine. The standard electrode potential is a measure of the tendency of a chemical species to acquire electrons and thereby be reduced. A higher standard electrode potential means a greater tendency to gain electrons, hence a stronger oxidising power.

In addition, the bond energy of Cl-Cl is lower than that of I-I. This means that it requires less energy to break a Cl-Cl bond than an I-I bond, making it easier for chlorine to accept an electron and become reduced.

In summary, chlorine's higher electronegativity, higher standard electrode potential, and lower bond energy compared to iodine all contribute to its stronger oxidising power.