Halogeeniryhmät

Halogeeniryhmät, or halogen groups, refer to the elements found in Group 17 of the periodic table. These elements are fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). They are characterized by having seven valence electrons, which makes them highly reactive.

Halogens are nonmetals, and in their elemental form, they exist as diatomic molecules (e.g., F2, Cl2, Br2, I2). Their physical states at room temperature vary: fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid. Astatine is a radioactive element and its properties are less well-understood.

Due to their high electronegativity, halogens readily gain one electron to form stable halide ions with a -1 charge. This property makes them strong oxidizing agents. They react vigorously with most metals to form ionic halide salts, such as sodium chloride (NaCl) and potassium bromide (KBr). They also react with nonmetals, often forming covalent compounds.

The reactivity of halogens decreases as you move down the group. Fluorine is the most reactive, followed by chlorine, bromine, and then iodine. This trend is consistent with their electronegativity values. Halogens play important roles in various industrial and biological processes, including disinfection, the production of plastics, and in the human body as essential electrolytes.