Halogeenarühmade

Halogeenarühmade refers to a group of chemical elements belonging to Group 17 of the periodic table, also known as the halogens. These elements include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Astatine is a rare and highly radioactive element, and its properties are less well-understood compared to the others. These elements are characterized by having seven valence electrons, meaning they are one electron short of achieving a stable electron configuration.

This electronic structure makes halogens highly reactive nonmetals. They readily gain one electron to form halide ions with a charge of -1. This tendency to form salts is the origin of their name, "halogens," which means "salt-forming" in Greek. In their elemental form, halogens exist as diatomic molecules, such as F₂, Cl₂, Br₂, and I₂. The physical state of halogens at room temperature varies: fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid.

Halogens exhibit a trend in reactivity and physical properties down the group. Reactivity generally decreases from fluorine to iodine, with fluorine being the most electronegative and reactive element. Their boiling and melting points increase as the atomic size increases. Halogens are important in various industrial and biological processes, forming compounds like sodium chloride (table salt) and playing roles in disinfectants, plastics, and pharmaceuticals.