Pronouncing chemical formulas

The number in front of each chemical formula can be read as a number of atoms and molecules (2 atoms of A1 and 3 molecules of Brg form 1 molecule of Al2Br6). It can refer equally as well to number of moles. Thus, the balanced equation for the reaction of aluminum and bromine tells us that 2 mol of solid aluminum reacts with 3 mol of liquid bromine to produce 1 mol of solid AlgBr . The relationship between the quantities of chemical reactants and products is called stoichiometry (pronounced stoy-key-AHM-uh-tree ), and the coefficients in a balanced equation are the stoichiometric coefficients. 

In this chapter we explore some important aspects of chemical reactions. Our focus will be both on the use of chemical formulas to represent reactions and on the quantitative information we can obtain about the amounts of substances involved in those reactions. Stoichiometry (pronounced stoy-key-OM-uh-tree) is the area of study that examines the quantities of substances consumed and produced in chemical reactions. Stoichiometry (Greek stoicheion, element, and metron, measure ) provides an essential set of tools widely used in chemistry, including such diverse applications as measuring ozone concentrations in the atmosphere and assessing different processes for converting coal into gaseous fuels. 

The most obvious feature of these C chemical shifts is that the closer the carbon is to the electronegative chlorine the more deshielded it is Peak assignments will not always be this easy but the correspondence with electronegativity is so pronounced that spec trum simulators are available that allow reliable prediction of chemical shifts from structural formulas These simulators are based on arithmetic formulas that combine experimentally derived chemical shift increments for the various structural units within a molecule... 

As noted earlier, more than one compound may have the same molecular formula (isomers), but a structural formula is unique to one compound. In addition, there are many chemicals which possess more than one chemical name, for the same reason mentioned above. The most common organic chemicals are those that have the shortest carbon chains. This fact is also true of their derivatives. The inclusion of a double bond in the structural formula has a profound effect on the properties of a compound. Table 2 illustrates those differences through the properties of alkenes. The presence of a double bond (and, indeed, a triple bond) between two carbon atoms in a hydrocarbon increases the chemical activity of the compound tremendously over its corresponding saturated hydrocarbon. The smaller the molecule (that is, the shorter the chain), the more pronounced this activity is. A case in point is the unsaturated hydrocarbon ethylene. Disregarding... 

In 1839, Eduard Simon, an apothecary in Berlin, distilled storax resin obtained from the Tree of Turkey , (liquid ambar orientalis) with a sodium carbonate solution and obtained an oil which he analysed and named styrol (what we now call styrene) [1]. He recorded the following observation that with old oil the residue which cannot be vaporised without decomposition is greater than with fresh oil, undoubtedly due to a steady conversion of the oil by air, light and heat to a rubberlike substance . Simon believed he had oxidised the material and called the product styrol oxide. Later, when he realised that it contained no oxygen, the product became known as metastyrol. This puzzled the early chemists as there was no change in empirical formula despite the very pronounced alteration in chemical and physical properties. Unknowingly, this was the first recorded instance of polymerization. 

In our description of the metal structures we have, of course, included many in which covalent or ionic binding predominates. Such systems may often quite properly be regarded as chemical compounds, but it is not in such systems that the chief interest lies, and here we shall discuss only the systems of more pronouncedly metallic character, including the electron compounds. It was early pointed out by Hume-Rothery that if formulae are assigned to such phases they must not be expected to obey the ordinary chemical valencies of the metals concerned. In fact, the satisfaction of chemical valencies is the negation of metallic properties... 

Constitution refers to the binding situation, i.e. the sequence of atoms in a molecule. Systems which have the same sum formula, but different structural formulae are called constitutional isomers. The transformation of one constitutional isomer into another requires breaking and forming chemical bonds with activation energies > 1 eV (96.5 kj/mol). Polymerization defects like head-head-addition (in place of the desired head-tail-addition) introduce constitutional isomers which sometimes have pronounced effects on the material properties. For simplicity however, an ideal, defect-free constitution of the systems inquired will be assumed throughout this review, and constitutional isomerism will not be discussed. 

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