Halogeeniyhmä

Halogeeniyhmä, known in English as the halogen group, refers to the elements found in Group 17 of the periodic table. These elements include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). The name "halogen" comes from Greek and means "salt-former," a nod to the fact that these elements readily react with metals to form salts.

Halogens are highly reactive nonmetals. Their reactivity stems from their electron configuration, which has seven valence electrons. They have a strong tendency to gain one electron to achieve a stable electron configuration, making them powerful oxidizing agents. This high reactivity means that halogens are rarely found in their pure elemental form in nature; instead, they exist as compounds. For example, chlorine is found in sodium chloride (table salt), and bromine is found in various bromide salts.

The physical properties of the halogens vary significantly with increasing atomic number. Fluorine is a pale yellow gas, chlorine is a greenish-yellow gas, bromine is a reddish-brown liquid, and iodine is a dark purple solid that sublimes into a violet vapor. Astatine is a rare, radioactive element with properties that are not as well-characterized, and tennessine is a synthetic, highly radioactive element. As atomic number increases, so does the melting and boiling point of these elements. Their electronegativity also decreases down the group.

Halogens play vital roles in various applications. Chlorine is used in disinfectants and to produce plastics. Fluorine is essential for dental health (in toothpaste) and is used in refrigerants and non-stick coatings. Bromine compounds are used in flame retardants and pharmaceuticals. Iodine is crucial for thyroid hormone production in living organisms.