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Learning ObjectivesTo know the periodic trends and reactivity of the group 17 elements: the halogens.
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Because the halogens are highly reactive, no one is uncovered in nature as the free element. Hydrochloric acid, i beg your pardon is a ingredient of aqua regia (a mixture of HCl and HNO3 that dissolves gold), and the mineral fluorspar (CaF2) were well known to albetterworld2016.orgists, who supplied them in their search for gold. In spite of their existence in acquainted substances, none of the halogens was even recognized as an facet until the 19th century.
Because the halogens are highly reactive, nobody is found in nature as the free element.
Chlorine to be the very first halogen come be obtained in pure form. In 1774, Carl Wilhelm Scheele (the codiscoverer of oxygen) produced chlorine by reacting hydrochloric acid v manganese dioxide. Scheele to be convinced, however, the the pale environment-friendly gas he collected over water to be a link of oxygen and also hydrochloric acid. In 1811, Scheele’s “compound” was determined as a new element, named from the Greek chloros, definition “yellowish green” (the very same stem as in chlorophyll, the environment-friendly pigment in plants). That very same year, a French industrial betterworld2016.orgist, young name Courtois, accidentally included too lot sulfuric acid to the residue obtained from burned seaweed. A deep violet vapor to be released, which had a biting aroma comparable to the of Scheele’s “compound.” The violet substance was identified as a brand-new element, called iodine native the Greek iodes, an interpretation “violet.” Bromine was found soon after by a young French betterworld2016.orgist, Antoine Jérôme Balard, who isolated a deep red liquid with a solid chlorine-like odor from brine native the salt marshes close to Montpellier in southern France. Due to the fact that many of its properties were intermediate between those the chlorine and also iodine, Balard originally thought he had isolated a compound of the 2 (perhaps ICl). He soon realized, however, that he had uncovered a new element, i beg your pardon he named bromine native the Greek bromos, definition “stench.” Currently, organic chlorine compounds, such as PVC (polyvinylchloride), consume around 70% the the Cl2 developed annually; organobromine link are provided in lot smaller quantities, primarily as fire retardants.
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Because that the distinctive properties of its compounds, fluorine was thought to exist long prior to it was actually isolated. The mineral fluorspar (now called fluorite