What are the properties of Group 7 elements and their halides?

Group 7 elements and their halides have distinct properties that make them important in biological systems.

Group 7 elements, also known as halogens, are highly reactive non-metals that exist as diatomic molecules in their elemental form. They have seven valence electrons, making them highly electronegative and able to form strong covalent bonds with other elements. As we move down the group, the atomic radius increases, and the electronegativity decreases. This trend is due to the increasing number of electron shells, which shield the outermost electrons from the nucleus.

Halogens readily form halides by gaining one electron to form a negative ion. Halides are important in biological systems as they are involved in the formation of ionic bonds, which are essential for maintaining the structure and function of biological molecules. For example, chloride ions are important in maintaining the pH and osmotic balance of cells, while iodide ions are essential for the synthesis of thyroid hormones.

The reactivity of halogens decreases as we move down the group, with fluorine being the most reactive and iodine being the least reactive. This trend is due to the decreasing electronegativity and increasing atomic radius. Halides also follow a similar trend, with fluorides being the most reactive and iodides being the least reactive. This trend is due to the decreasing size of the anion, which makes it harder for the anion to attract a cation.

In summary, Group 7 elements and their halides have distinct properties that make them important in biological systems. The reactivity and size of these elements and their halides follow predictable trends that can be used to understand their behaviour in biological systems.