Group+17+Halogens

=Halogens=

The halogens (coming from the Greek words //halos//, "salt," and //gennao//, "production") are the Group 17 nonmetal elements fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the rare element astatine (At) (which won't be included in the following information). Some recent classifications include the undiscovered 117th element ununseptium as a halogen. These elements are highly reactive and can only be found in the environment as compounds or in their diatomic state, since every halogen is diatomic. This group is the only group in the periodic table to contain elements of all states of matter at room temperature (F and Cl are gases, Br is liquid, and I is solid). Halogens also form particularly strong acids, known as hydrohalic acids (except for fluorine). The halogens follow almost all of the periodic trends. For example, they all end in a p5 subshell, making their ionic charge -1. The halogen's atomic radii increase going down the group. First ionization energy decreases going down the group. The halides decrease in electronegativity going down the group.

Fluorine is the most reactive of all the halogens, and can even take electrons away from water. It naturally occurs as a poisonous, yellowish-brown gas. Fluorine was first used on a large-scale during the Manhattan project.

Chlorine is a poisonous, yellowish-green gas. As a powerful oxidant, it is used in bleach and disinfectants, most commonly in swimming pools.

Bromine is a red, volatile liquid, one of the only two elements naturally occurring as a liquid. Pure bromine is a corrosive liquid and a toxic gas. When combined to form brominated vegetable oil, it is commonly used in citrus-flavored soda pop. Bromine also has many manufacturing applications.

Iodine, a solid, is most commonly found dissolved in seawater, although it is also present in minerals. Iodine is commonly used in pharmaceuticals, anti-septics, and medicine.

Sources: [|http://en.wikipedia.org] Brown, LeMay, and Bursten: //Chemistry, the Central Science// [|www.webelements.com]

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