Halides elemental hydrogen

Reactions of Hydrogen and Other Elements. Hydrogen forms compounds with almost every other element. Direct reaction of the elements is possible in many cases. Hydrogen combines direcdy with the halogens, X2, to form the corresponding hydrogen halide. 

Silylated triphosphanes and triphosphides, synthesis, 31 188-194 yields, 31 194 Silylenes, 29 2-6 addition reactions, 29 4-6 to butadiene, 29 4 to ethylene, 29 4 to hexadienes, 29 5 mechanism, 29 4 nitric oxide scavenging, 29 4 complexes, 25 37, 51, 116, 118 as catalyst intermediates, 25 118 extrusion from disilanes, 25 114, 118 halides, 3 225 from hydridosilanes, 25 14 insertion into element-hydrogen bonds, 29 3-4... 

Occurrence, extraction and uses Physical properties The elements Hydrogen halides... 

Like the Group 7A(17) elements, hydrogen occurs as diatomic molecules and fills its outer (valence) level either by electron sharing or by gaining one electron from a metal to form an anion (hydride, H ) with a 1- charge. However, while the monatomic halide ions (X ) are common and stable, the H ion is rare and reactive. 

Reactivity of the elements Hydrogen halides Interhalogens Polyhalogen cations Polyhalide anions Oxides and oxoacids Aqueous solution chemistry... 

The unequal distribution of charge produced when elements of different electronegativities combine causes a polarity of the covalent bond joining them and, unless this polarity is balanced by an equal and opposite polarity, the molecule will be a dipole and have a dipole moment (for example, a hydrogen halide). Carbon tetrachloride is one of a relatively few examples in which a strong polarity does not result in a molecular dipole. It has a tetrahedral configuration... 

For the formation of the hydrogen halides by the direct combination of the elements, the enthalpies of formation are ... 

Anhydrous halides, however, are obtained when the metal is heated with the dry hydrogen halide or the halogen. In the case of elements with more than one oxidation state, the hydrogen halide produces a lower halide and the halogen a higher halide, for example... 

Preparation of Uranium Metal. Uranium is a highly electropositive element, and extremely difficult to reduce. As such, elemental uranium caimot be prepared by reduction with hydrogen. Instead, uranium metal must be prepared using a number of rather forcing conditions. Uranium metal can be prepared by reduction of uranium oxides (UO2 [1344-59-8] or UO [1344-58-7] with strongly electropositive elements (Ca, Mg, Na), reduction of uranium halides (UCl [10025-93-1], UCl [10026-10-5] UF [10049-14-6] with electropositive metals (Li, Na, Mg, Ca, Ba), electro deposition from molten... 

Nonmetal haUdes are generally hydroly2ed to a hydrogen haUde and to an oxy-acid containing the other element. The first row nonmetal haUdes, eg, CCI4, resist hydrolysis because the nonmetal element cannot expand its octet of electrons to form a bond to water before its bond to the haUde is broken. Hydrolysis requires either an energetic water molecule to strike the haUde or ioni2ation of the covalent nonmetal—halide bond, processes that tend to be quite slow (16). 

The hydrogen halides, HX, can be prepared by the direct reaction of the elements ... 

Reduction is a chemical reaction in which an element gains an electron, in other words, when the oxidation state is lowered. Reduction reactions are widely used, particularly the hydrogen reduction of the halides, as shown in the following examples ... 

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