Vertical columns on the periodic table are known as groups, and these groupings contain elements that share similar chemical properties. Group 17, located toward the right side of the table, represents a highly reactive family of nonmetals that are uniquely important in chemistry and everyday life. These elements are characterized by their strong tendency to combine with other substances.
Group 17’s Official Name
The elements in Group 17 are officially known as Halogens. This term is derived from two Greek roots: hal-, meaning “salt,” and -gen, meaning “to form” or “to produce.” The name literally translates to “salt-former.” This name is chemically appropriate because halogens readily react with metals, such as sodium, to produce a wide range of salts. The most common example is the formation of sodium chloride, or table salt, from the reaction between sodium metal and chlorine gas.
The Defining Chemical Feature
The high reactivity and salt-forming tendency of the halogens are rooted in their specific electron configuration. All elements in Group 17 possess seven electrons in their valence shell. This arrangement is just one electron short of the stable, full-shell configuration known as an octet. Because of this deficit, halogens have a strong drive to gain a single electron to achieve that stable octet. This powerful attraction for an extra electron results in high electronegativity, making them strong oxidizing agents. When they acquire this electron, they form a stable negative ion with a charge of -1, known as a halide ion.
Common Elements and Their Uses
The most well-known halogens include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). Fluorine and chlorine exist as gases, bromine is a liquid, and iodine is a dark solid. This physical diversity does not hinder their shared chemical utility.
The halogens have several important applications:
- Fluorine is used in water fluoridation and incorporated into toothpaste as sodium fluoride to help prevent tooth decay.
- Chlorine’s strong oxidizing ability makes it a primary agent for disinfecting swimming pools and purifying public drinking water supplies.
- Bromine compounds are utilized in the production of flame retardants.
- Iodine, in the form of tincture of iodine, is a common antiseptic applied to minor wounds and is also an important dietary supplement added to table salt to prevent deficiency.