| MadSci Network: Chemistry |
The property that makes halogens unique is that these elements contain 7 electrons in their in the outermost shell. A halogen atom must acquire one electron through combination with other elements in order to attain an outer octet of electrons and become a halogenide ion. Since the atoms of these elements are so strongly electronegative, they are all active elements which have never been found free in nature.What makes them "halogens" and not "noble gases" or "alkoid metals" or something else?They are called halogens, from the Greek words meaning salt producers, because halogens are very active nonmetals and they readily form salts such as sodium chloride, by simple chemical combination with metals. Unlike noble gases with the exception of helium atoms, which have a pair of electrons as their outer shell, atoms of noble gases have an octet as their outer shell. This is the greatest number of electrons found in the outer shell which makes them generally chemically inert.
Try the links in the MadSci Library for more information on Chemistry.