Halogens


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Halogens

 

the chemical elements fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At), which form the main subgroup of Group VII of the Mendeleev periodic system. They are called halogens (from the Greek hals, salt) because they form salts (for example, common salt, NaCl) upon combination with metals. The name “halides” is sometimes used. There are seven electrons (configuration s2p5) in the outer electron shell of the halogen atoms, that is, they are one electron short of the stable eight-electron inert-gas configuration (s2p6). Upon reacting with a metal, each halogen atom removes an electron from it, thus showing oxidizing properties. All halogens are very reactive, combining directly with most chemical elements. The chemical reactivity of halogens decreases from fluorine to iodine as the atomic radius increases. Under ordinary conditions fluorine and chlorine are gases, bromine is a liquid, and iodine and astatine are solids. Astatine is a radioactive element. The molecules of the halogens are diatomic.

References in periodicals archive ?
Rather than replace halogens with potentially equally harmful substitutes, it would be more logical and effective to address this issue at the e-waste sites.
The first thing to do is to get rid of your halogen torchieres," says Jennifer Thorne, an ACEEE research associate.
Again, it begins with the polar sunrise and continues through the austral spring when generation of airborne halogens is high.
The goal is to lower total halogen levels and increase uv stability.
The halogens used suppress polymer fires in the listed order iodine > bromine > chlorine > fluorine.
In broad terms, halogens are associated with PWBs and components, while halides are associated with soldering operations.
Forecasts are included by wattage and application for various lighting technologies including CCFL, CFL, HID, Linear Fluorescent, LED, and Halogen.
Says Monsanto's Mount, "There's a bit of movement currently to get halogen out of these systems.
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Halogens tend to produce a more gradual shift from light to dark.
corner of Pearl & Morton) to show the extreme temperatures halogen lamps can reach.
based in Clearwater, manufactures and markets patent and patent-pending proprietary ionization disinfection technologies that substantially reduce or replace halogens (chlorine) completely.