Halogen family of elements

Iodine is the heaviest of the halogen family of elements, excluding the radioactive element astatine. It was discovered in 1811 by French chemist Bernard Courtois, who isolated the element from seaweed. The element is named for its color in the gas phase (the Greek word iodes means violet ). 

Chlorine is one of the halogen family of elements and the first of that family to be discovered. Swedish chemist Carl Wilhelm Scheele prodnced chlorine in 1774 by the reaction of manganese dioxide (Mn02) with a solntion of hydrochloric acid (HCl). In 1810 English chemist Sir Hnmphry Davy determined chlorine to be an element and named it for the color of the gas (the Greek word chloros means pale green ). 

The person whose name is most closely associated with the periodic table is Dmitri Mendeleev (1836-1907), a Russian chemist. In writing a textbook of general chemistry, Mendeleev devoted separate chapters to families of elements with similar properties, including the alkali metals, the alkaline earth metals, and the halogens. Reflecting on the properties of these and other elements, he proposed in 1869 a primitive version of today s periodic table. Mendeleev shrewdly left empty spaces in his table for new elements yet to be discovered. Indeed, he predicted detailed properties for three such elements (scandium, gallium, and germanium). By 1886 all of these elements had been discovered and found to have properties very similar to those he had predicted. 

The halogens are a family of elements appearing on the right side of the periodic table, in the column just before the inert gases. The elements in this group—fluorine, chlorine, bromine, iodine, and astatine—show some remarkable similarities and some interesting trends in chemical behavior. The similarities are expected since the... 

Figure 4.2. The Periodic Table special collective names. The informal symbols of these families of elements are A = alkali metals, Ae = alcaline earth metals, Ln = lanthanides R = rare earth metals = Sc + Y + lanthanides, An = actinides, Hal = halogens, Chal = chalcogens,...

Bromine is a member of a family of elements known as halogens that are found in group 7A of the Periodic Table. Bromine was discovered in 1826 in Montpelher, France, by French chemist Antoine J. Balard. 

The two most reactive families of elements are the halogens and the alkali metals. How do they differ in their reactivities ... 

The fact that x(0) and k tend to vary inversely means that atomic properties related to electronegativity may sometimes not change monotonically within a family of elements. A number of examples of this have been observed and discussed [13-16,19-24]. For instance, in a recent computational study of the electrostatic potentials associated with naphthalene derivatives, we found evidence that the electron-attracting tendencies of the halogens in 1-halonaphtha-lenes increase in the order F < Br < Cl [24]. 

A family of elements is a numbered group from the periodic table, sometimes carrying a distinctive name. For example, group 17 is the halogen family. 

Iodine [7553-56-2] I, atomic number 53, atomic weight 126.9044, is a nonmetaUic element belonging to the halogen family in Group 17 (VIIA) of the Periodic Table. The only stable isotope has a mass number of 127. There are 22 other iodine isotopes having masses between 117 and 139 14 of these isotopes yield significant radiation. 

Most of the reactions of the halogens are of the oxidation-reduction type. The halogens are so reactive that they do not occur uncombined in nature and they must be made from halide compounds (salts). We shall consider briefly the preparation of the elements and then explore some of the very interesting chemistry of this family. 

Heteroboranes are those in which one or more non-boron atoms replace a BH vertex, together with groups that may be attached to these heteroatoms. Boranes that contain CH vertices constitute the vast family of carbaboranes. The possibility for carbon to participate in electron-deficient frameworks contradicted the former prejudice of the always electron-precise carbon as the well-behaved brother of naughty boron. So far, most elements have been introduced as heteroatoms into borane frameworks, with the exception of the halogens and the noble gases. 

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