Symbols for Commonly Used Physical Quantities

Charge number of an ion Conductivity Diffusion rate constant Electric current Electric current density Electric mobility Electrode potential Electrolytic conductivity Electromotive force (emf) Elementary charge Faraday constant Half-wave potential Ionic strength 

Amount concentration Amount of substance Atomic weight Concentration Degree of dissociation 

Bohr magneton Bohr radius Chemical shift, 8 scale Coupling constant (indirect) spin-spin direct (dipolar) reduced spin-spin Delay time 

Electron spin quantum component Electron spin quantum number Hyperhne coupling constant Larmor angular frequency Larmor frequency Magnetogyric ratio Nuclear magneton Nuclear spin quantum component Nuclear spin quantum number Orbital quantum number Orbital quantum number component Principal quantum number Quadrupole moment Relaxation time longitudinal transverse Shielding constant 

NAME Absorbance Absorption factor Angle of optical rotation Angular frequency Emissivity, emittance Frequency 

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This chapter presents a quick reference guide for the use of typefaces (roman, italic, and bold), Greek letters, superscripts and subscripts, and special symbols that are commonly used in chemistry. Appendix 13-1 presents the symbols for commonly used physical quantities. 

Symbols for Commonly Used Physical Quantities / 269 Acknowledgments / 279... 

Ordinarily, the same symbol is used for a given physical quantity regardless of its units. Subscripts, superscripts, and lower- and upper-case letters can be employed to give special meanings. The nomenclature should be consistent with common usage (a list of recommended symbols for chemical engineering quantities is presented in Table l).t... 

In the past, several systems of metric units were commonly used by scientists, each system having its advantages and disadvantages. Recently international agreement was reached on the use of a single set of units for the various physical quantities, as well as on a recommended set of symbols for the units and for the physical quantities themselves. The SI will be used in this book with only a few additions. Because of its importance in defining the standard state of pressure, the atmosphere will be retained as a unit of pressure in... 

Table 1 shows some symbols and abbreviations commonly used in analytical chemistry Table 2 shows some of the alternative methods for expressing the values of physical quantities and the relationship to the value in SI units. 

If a substance undergoes a transformation from one physical stale to another, such as a polymorphic transition, the fusion or sublimation of a solid, or the vaporization of a liquid, the heat adsorbed hy the substance during the transformation is defined as the latent heat of transformation (transition, fusion, sublimation or vaporization). It is equal in the enthalpy change of the process, which is the difference between the enthalpy of the substance in the two states at (he temperature of the transformation. For the purpose of thcrmochemical calculations, i( is usually reported as a molar quantity with die units of calories (or kilocalories) per mule (or gram formula weight). The symbol L or AH. with a subscript i.f (or in), s. and n is commonly used and the value is usually given at the equilibrium temperature of the transformation under atmospheric pressure, or at 25 C. 

Listed below are the most common meanings of those symbols that occnr freqnently in this book special usages of these symbols and the meanings of any nnlisted symbols are defined in the text wherever they occnr. Symbols used to represent nnits for physical quantities are given in Appendix B. A more complete listing of symbols is given in 1. Mills et. al., Quantities, Units and Symbols in Physical Chemistry, 2d ed., pnblished for lUPAC by Blackwell, Oxford (1993). 

The metric system, or International System (SI, from Systlme International), is a decimal system of units for measurements of mass, length, time, and other physical quantities. Built around a set of standard units, the metric system uses factors of 10 to express larger or smaller numbers of these units. To express quantities that are larger or smaller than the standard units, prefixes are added to the names of the units. These prefixes represent multiples of 10, making the metric system a decimal system of measurements. Table 2.1 shows the names, symbols, and numerical values of the common prefixes. Some examples of the more commonly used prefixes are... 

It is convenient to define a system of units that is more natural for working with atoms and molecules. The commonly accepted system of atomic units for some important quantities is summarized in Table 4-1. [Note the symbol h ( h-cross or h-bar ) is often used in place of hlln.] Additional data on values of physical quantities, units, and conversion factors can be found in Appendix 10. 

Chemical species and units of physical quantities are denoted by Roman type characters, whereas physical quantities that can be expressed by numerical values are denoted by Greek or italic characters. Mathematical symbols have their usual meaning and are not listed here. The same symbol is used for an extensive property of a system and for the molar quantity of a constituent of the system. The SI system of physical units is used throughout, but some extra SI units commonly used in the physicochemical literature are also included where they simplify the notation. These include the symbols °C for centigrade temperatures (T/K-273.15), M for mol-dm , and m for mol (kg solvent)". ... 

A brief mention should be made about the terminology that has been used in the literature on the compressibilities of solutes in solution. The lUPAC "Quantities, Units and Symbols in Physical Chemistry" [93M] recommends that the name for the thermodynamic quantity Pt (or Ps) is the isothermal (or isentropic) compressibility. It also recommends that k is the symbol used to represent this quantity. In the chemical literature both and Px have been used as the symbols for the quantity -(l/V)(8V/8p)x, where x is either T or S, but in the biochemical literature Px has been used almost exclusively. For this reason we have chosen to use px in this review. The quantity Ps has sometimes been referred to as the adiabatic compressibility. The term adiabatic is loosely used in this context because isentropic does not mean adiabatic but adiabatic and reversible. The word compressibility has also been used in the chemical literature to name the thermodynamic quantity Kj,2 (Kt,2 = -(3V2/3p)x) which is commonly referred to as the partial molar isothermal compressibility. Similarly, in the study of protein solutions the same name has appeared in the biochemical literature to describe two different thermodynamic quantities. Both P and... 

The symbols and terminology for physicochemical quantities and units are those recommended by lUPAC through its Physical Chemistry Division. For the thermodynamic notation needed but not specified by these two sources, the recommendations of the Bulletin of Chemical Thermodynamics are used. Similarly, for spectroscopic nomenclature, the common practice of Moore and Herz-berg " is followed. 

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