The name "halogen" is derived from the Greek roots hal- ("salt") and -gen ("to form"). Halogen elements can cross-link to form diatomic molecules with polar covalent single bonds.Ĭhlorine (Cl 2) was the first halogen to be discovered in 1774, followed by iodine (I 2), bromine (Br 2), fluorine (F 2), and astatine (At, discovered last in 1940). When a halogen atom is substituted for a covalently-bonded hydrogen atom in an organic compound, the prefix halo- can be used in a general sense, or the prefixes fluoro-, chloro-, bromo-, or iodo- can be used for specific halogen substitutions. The halogens often form single bonds, when in the -1 oxidation state, with carbon or nitrogen in organic compounds. Therefore, most of the chemical reactions that involve halogens are oxidation-reduction reactions in aqueous solution. Replacing the -ine ending with an -ide ending indicates the presence of halide anions for example, Cl - is named "chloride." In addition, halogens act as oxidizing agents-they exhibit the property to oxidize metals. In these compounds, halogens are present as halide anions with charge of -1 (e.g. All halogens form Group 1 salts with similar properties. As a general rule, fluorine is the most reactive halogen and astatine is the least reactive. However, halogens readily combine with most elements and are never seen uncombined in nature. The bonds in these diatomic molecules are non-polar covalent single bonds. Halogens form diatomic molecules (of the form X 2, where X denotes a halogen atom) in their elemental states. ![]() This characteristic makes them more reactive than other non-metal groups. Because the halogen elements have seven valence electrons, they only require one additional electron to form a full octet. Although astatine is radioactive and only has short-lived isotopes, it behaves similar to iodine and is often included in the halogen group. These five toxic, non-metallic elements make up Group 17 of the periodic table and consist of: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). The halogens are located on the left of the noble gases on the periodic table. Oxidation States of Halogens in Compounds.Reactivity of Elements (decreases down the group).Electron Affinity (decreases down the group).Electronegativity (decreases down the group).Ionization Energy (decreases down the group).Atomic Radius (increases down the group).Melting and Boiling Points (increases down the group).Some are fitted with halogen bulbs for overall punch, or spots to light specific objects or to highlight.\).Roma table Grillo low-voltage tungsten halogen lamp with dimmer switch.Another type of light bulb you may come across is the tungsten halogen bulb. ![]()
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