22.4+Group+VIIA+The+Halogens


 * __Chapter 22.4 Group 7A: The Halogens__**

Properties

The halogens- F, Cl, Br, I, At- are all diatomic molecules under standard conditions. Fluorine and chlorine both exist as gases. Bromine exists as a liquid and astatine and iodine as solids and are all held togther by London dispersion forces. All of the halogens have outer electron configurations of ns2np5, enabling them to acquire a -1 oxidation state due to the ability to achieve a noble gas electron configuration.



__Fluorine__
 * Fluorine is the most reactive of the halogens. It has many practical purposes such as use in refrigerants, plastics, and Teflon- a substance produced entirely from carbon and fluorine and is used on the surfaces of cooking ware as a nonstick coating and as a friction reducer in many industrial applications.

__Chlorine__
 * Chlorine is the most important industrial halogen. It is used to make PVC pipe and in bleach to kill bacteria.

__Iodine__ __Bromine__ __Astatine__
 * Iodine is incorporated into table salt in order to provide us with our daily value. It is a necessary element that is utilized by the thyroid gland to produce the hormone thyroxin.
 * Bromine is the only nonmetalic element that is liquid at room temperature. It causes painful burns if it comes into contact with the skin. It is mostly used in pesticides and as an anti-knockout source in certian poisonous liquids such as gasoline.
 * Astatine is very radioactive and has very short half lives. Not much is known about astatine because it is so rarely present that it is almost as if it is not there at all.

Just a fun little song to help remember the properties above! media type="youtube" key="Qvs4NTB71uY" height="390" width="480" [] Hydrogen Halides

When the halogens are combined with hydrogen, they form stable diatomic molecules. When hydrogen and iodine, chlorine, or bromine is dissolved in water, a strong acid is formed. HF is a weak acid due to the negative change in entropy that occurs when it is formed and therefore does not favor the formation of HF.

Interhalogen Compounds

When a compound is formed between two halogens, it is called an interhalogen compound, or interhalide. The interhalogen compounds are very strong oxidizing agents. These interhalides follow the formula of ABn, where the larger of the two halogens is A, the smaller, B and n can be either 1, 3, 5, or 7.

Oxyacids and Oxyanions

The formation of an oxyacid is formed from the reaction between a nonmetal oxide and water. As the oxidation state of the central halogen atom increases, the acid strength increases. An oxyanion is the formation of an element with oxygen. They are typically formed by removing the hydrogen ion from an oxyacid, and are more stable than oxyacids.
 * Relationship || Central Atom Oxidation Number || Naming Formula || Example ||
 * one more oxygen than root || = group # || per(root)ate || ClO4- (Perchlorate) ||
 * one oxygen atom || = group # - 2 || (root)ate || ClO3- (Chlorate) ||
 * one less oxygen than root || = group # - 4 || (root)ite || ClO2- (Chlorite) ||
 * two less oxygen than root || = group # - 6 || hypo(root)ite || ClO- (Hypochlorite) ||

[|Visual Elements- Group 17 The Halogens] [|Naming Oxyacids] [|Naming Oxyanions] "Astatine (At) - Chemical Properties, Health and Environmental Effects." //Lenntech//. Web. 23 Mar. 2011. . Bishop, Mark. "Oxyanions." //An Introduction to Chemistry//. Web. 23 Mar. 2011. <[].> Tro, Nivaldo J. "22.9 Halogens: Reactive Elements with High Electronegativity." Chemistry: A Molecular Approach. Upper Saddle River: Pearson Education, 2008. 1017-021. Print."Oxyacid." //Encyclopædia Britannica. Encyclopædia Britannica Online//. Encyclopædia Britannica, 2011. Web. 22 Mar. 2011. [| Zumdahl, Steven S. "Oxyacid (Chemical Compound)." //Encyclopedia - Britannica Online Encyclopedia//. Web. 22 Mar. 2011. <[]> Zumdahl, Steven S., and Susan A. Zumdahl. "The Group 7A Elements." Chemistry. Sixth ed. Boston: Houghton Mifflin, 2003. 967-73. Print.
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