Discuss the properties and reactivity trends of... - SS3 Chemistry Inorganic Chemistry: p-Block Elements Question

Group 17 elements, known as the Halogens, include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). These elements share several common properties and reactivity trends.

Properties and Reactivity Trends:

1.    Atomic Structure: Halogens have seven valence electrons in their outermost energy level, leading to an oxidation state of -1. They tend to gain one electron to achieve a stable noble gas electron configuration.

2.    Electronegativity: Electronegativity decreases slightly from fluorine to iodine due to the increase in atomic size. However, they remain highly electronegative, making them powerful oxidising agents.

3.    Physical State: Fluorine and chlorine are gases at room temperature, bromine is a liquid, and iodine is a solid. This trend reflects the gradual increase in molecular size down the group.

4.    Reactivity: Halogens exhibit a trend of decreasing reactivity down the group. Fluorine is the most reactive halogen and can even react with noble gases. Chlorine is a strong oxidising agent and is commonly used in water treatment. Bromine is less reactive and often used in flame retardants, while iodine's reactivity is lower, making it suitable for medical disinfectants.

Role in Compound Formation and Daily Life:

Halogens readily form compounds with metals, known as metal halides, and with nonmetals, known as covalent halides. Some common examples include:

●     Sodium chloride (NaCl): Common table salt used in cooking and food preservation.

●     Hydrogen fluoride (HF): Used in the production of fluorine-containing compounds and etching glass.

●     Chlorofluorocarbons (CFCs): Used as refrigerants and aerosol propellants, although their use is now largely restricted due to their negative impact on the ozone layer.

●     Iodine-containing antiseptics: Used for disinfecting wounds and as a topical treatment for skin infections.

Furthermore, halogens play a critical role in biological systems. Iodine, for instance, is an essential element for the synthesis of thyroid hormones, which regulate metabolism. Fluoride is commonly added to drinking water to prevent tooth decay.