Fundamental Constants and Conversion of Units

In the metric system, three familiar basic units are the gram, the meter, and the second, and their symbols are g, m, and s, respectively. Their sizes are defined by international agreement to very high precision. Prefixes are used to designate units that are smaller by powers of 10 or larger by powers of 10. For each prefix, a symbol is attached to the unit symbol. A kilogram is 1000 g and its symbol is kg. The commonly encountered prefixes in chemical physics are the following. 

Metric Prefix (Symbol) Means the Prefixed Unit Is Scaled by 

Two traditional selections of a basic unit for mass, length, and time are often encountered. The mks form uses meters, kilograms, and seconds. The mks energy unit, called the joule 

The cgs form uses centimeters, grams, and seconds. The cgs energy unit is the erg  

The conversion between mks and cgs for any other physical quantities is obtained in a like manner. 

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Some useful conversion factors involving energy and mass units are summarized in Table 1.2 for a more detailed listing of fundamental constants and conversion factors see Appendix (Tables A.l and A.2). 

The system of atomic units was developed to simplify mathematical equations by setting many fundamental constants equal to 1. This is a means for theorists to save on pencil lead and thus possible errors. It also reduces the amount of computer time necessary to perform chemical computations, which can be considerable. The third advantage is that any changes in the measured values of physical constants do not affect the theoretical results. Some theorists work entirely in atomic units, but many researchers convert the theoretical results into more familiar unit systems. Table 2.1 gives some conversion factors for atomic units. 

Section 2 combines the former separate section on Mathematics with the material involving General Information and Conversion Tables. The fundamental physical constants reflect values recommended in 1986. Physical and chemical symbols and definitions have undergone extensive revision and expansion. Presented in 14 categories, the entries follow recommendations published in 1988 by the lUPAC. The table of abbreviations and standard letter symbols provides, in a sense, an alphabetical index to the foregoing tables. The table of conversion factors has been modified in view of recent data and inclusion of SI units cross-entries for archaic or unusual entries have been curtailed. 

The relation of atomic units to the corresponding SI units involves the values of the fundamental physical constants, and is therefore not exact. The numerical values in the table are based on the estimates of the fundamental constants given in chapter 5. The numerical results of calculations in theoretical chemistry are frequently quoted in atomic units, or as numerical values in the form (physical quantity)/(atomic unit), so that the reader may make the conversion using the current best estimates of the physical constants. 

Presented in this appendix are a list of basic and derived SI units, some fundamental constants frequently required by inorganic chemists, and some useful conversion factors. 

State functions derivable therefrom (such as ASd or AHd) are the fundamental quantities of interest, the arbitrariness of K or Kq causes no difficulty other than being a nuisance. It should be remembered that, once a choice of units and of standard state has been made, a value of /C or 1 implies that AG is a large negative quantity, and hence, that AGd is also likely to be large and negative. Thus, equilibrium will be established after the pertinent reaction has proceeded nearly to completion in the direction as written. Conversely, for values of K, or Kq equilibrium sets in when the reaction is close to completion in the opposite direction. Thus, the equilibrium constant serves as an index of how far and in what direction a reaction will proceed, and this prediction does not depend on the arbitrariness discussed earlier. It should be clear that the equilibrium constants do not in themselves possess the same fundamental importance as the differential Gibbs free energies. However, the full utility of equilibrium constants will not become clear until some illustrative examples are provided below. 

This chapter outlines and lists the symbols, terminology and nomenclature, the units and conversion factors, the order of formulae, the standard conditions, and the fundamental physical constants used in this volume. They are derived from international standards and have been specially adjusted for the TDB publications. 

These equations allow, for example, expressing the energy in temperature units or energy-equivalent mass units. During the conversion, however, the precision inherent in the values of the fundamental constants involved must be kept as much as possible and care should be taken of the correlation of uncertainties. For this reason, the safest procedure is to use the set of... 

This book provides a handy and convenient source of formulas, conversion factors and constants for students and professionals in engineering, chemistry, mathematics and physics. Section 1 covers the fundamental tools of mathematics needed in all areas of the physical sciences. Section 2 summarizes the SI system (International System of Units of measurement), lists conversion factors and gives precise values of fundamental constants. Sections 3 and 4 review the basic terms of spectroscopy, atomic structure and wave mechanics. These sections serve as a guide to the interpretation of modem literature. Section 5 is a resource for work in the laboratory, listing data and formulas needed in connection with frequently used equipment such as vacuum systems and electronic devices. Material constants and other data are listed for information and as an aid for estimates or problem solving. 

Baum, E. M., H. D. Knox, and T. R. Miller. 2010. Chart of the Nuclides, 17th ed. New York Knolls Atomic Power Laboratory, Lockheed Martin. Available as either a wall chart or a textbook version, this publication shows the key nuclear properties of the known stable and radioactive forms of the elements. In chart format, the nuchdes are arranged with the atomic number along the vertical axis and the neutron number along the horizontal axis. Descriptive information includes a history of the development of the periodic table, descriptions of the type of data on the chart, and unit conversion factors and fundamental physics constants. 

Table 1.2 lists the basic quantities as expressed in SI together with the unit abbreviations, Table 1,3 lists the unit prefixes needed for this book, and Table 1.4 lists some of the constants needed in several systems. Finally, Table 1.5 lists the conversion factors into SI for all quantities needed for this book. The boldface letters for each quantity represent the fundamental dimensions F = force, L = length, M = mass, mole = mole, T = temperature, 0 = time. The list of notation at the end of each chapter gives the symbols used, their meaning, and dimensions. 

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