Units and Their Abbreviations

In the examples given in the preceding section, both British and metric units were used. For example, the mile is a British unit of distance, while the meter is a metric unit kilogram is metric units of time, e.g., the second, are both British and metric. Science, however, tends almost exclusively to use the metric system, and that will be the general practice in this book. 

By international agreement scientists use almost exclusively the International System of Units (Syst me International d Unit s, or SI, in French). The fundamental units that are used, and their abbreviations, are the following  

For more than a century the world s standard kilogram has been a cylinder made of 90 percent platinum and 10 percent iridium (by weight) kept in Paris. Beginning in the 1790s, the world s standard meter was defined as one ten-millionth of the distance from the equator to the North Pole. In 1984, the definition of a meter was made more precise-l/299,792,458 the distance that light travels in a vacuum in one second. 

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Most cells are microscopic, invisible to the unaided eye. Animal and plant cells are typically 5 to 100 pm in diameter, and many bacteria are only 1 to 2 pm long (see the inside back cover for information on units and their abbreviations). What limits the dimensions of a cell The lower limit is probably set by the minimum number of each type of biomolecule required by the cell. The smallest cells, certain bacteria known as mycoplasmas, are 300 nm in diameter and have a volume of about 10 14 mb. A single bacterial ribosome is about 20 nm in its longest dimension, so a few ribosomes take up a substantial fraction of the volume in a mycoplasmal cell. 

Use the International System of Measurements (SI) base units and their abbreviations to describe length, mass, time, temperature, and volume. 

Write the metric base units and their abbreviations for length, mass, and volume. (See Section 1.4.)... 

A further complication to the molarity/molality confusion is how to distinguish between their variables and units. The letter m turns out to be overused in chemistry. Instead of picking another Vciriable (or perhaps a less confusing ncime that stcirted with a nice uncommon letter like z, chemists decided to give molality the lowercase script m as its variable. To help you avoid uttering cmy four-letter words when confronted with this plethora of m-words and their abbreviations, we ve provided Table 13-1. 

There are seven base units in SI. A base unit is a defined unit in a system of measurement that is based on an object or event in the physical world. A base unit is independent of other units. Table 2-1 hsts the seven SI base units, the quantities they measure, and their abbreviations. Some familiar quantities that are expressed in base units are time, length, mass, and temperature. 

The nutritional calorie of the weight watcher is actually 1000 scientific calories, or 1 kcal. It is represented by writing calorie with a capital C (Calorie, abbreviated Cal). Table 1.3 contains a list of the commonly used metric units, their relationship to basic units, and their relationship to English units. 

The seven SI base units and their standard abbreviated symbols are listed in Figure 2.1. All the other SI units can be derived from these seven fundamental units. 

It is never wrong to use only the fundamental units. In many situations that just means the numbers are either very large or very small. To keep numbers to reasonable sizes, scientists use units derived from the fundamental set of units using metric prefixes. These prefixes and their abbreviations are the following ... 

Units may be combined together into derived units to express a property more complicated than mass, length, or time. For example, volume, V, the amount of space occupied by a substance, is the product of three lengths therefore, the derived unit of volume is (meter)3, denoted m3. Similarly, density, the mass of a sample divided by its volume, is expressed in terms of the base unit for mass divided by the derived unit for volume—namely, kilogram/(meter)3, denoted kg/m3 or, equivalently, kg-m-3. The SI convention is that a power, such as the 3 in cm3, refers to the unit and its multiple. That is, cm3 should be interpreted as (cm)3 or 10-6 m3 not as c(m3), or 10 2 m3. Many of the more common derived units have names and abbreviations of their own. 

The units we use in daily life, such as kilogram (or pound) and meter (or inch) are tailored to the human scale. In the world of quantum mechanics, however, these units would lead to inconvenient numbers. For example, the mass of the electron is 9.1095 X J0 31 kg and the radius of the first circular orbit of the hydrogen atom in Bohr s theory, the Bohr radius, is 5.2918 X 10 11 m. Atomic units, usually abbreviated as au, are introduced to eliminate the need to work with these awkward numbers, which result from the arbitrary units of our macroscopic world. The atomic unit of length is equal to the length of the Bohr radius, that is, 5.2918 X 10 n m, and is called the bohr. Thus 1 bohr = 5.2918 X 10"11 m. The atomic unit of mass is the rest mass of the electron, and the atomic unit of charge is the charge of an electron. Atomic units for these and some other quantities and their values in SI units are summarized in the accompanying table. 

Scientists measure many different quantities—length, volume, mass (weight), electric current, temperature, pressure, force, magnetic field intensity, radioactivity, and many others. The metric system and its recent extension, Systeme International d Unites (SI), were devised to make measurements and calculations as simple as possible. In this chapter, length, area, volume, and mass will be introduced. Temperature will be introduced in Sec. 2.7 and used extensively in Chap. 11. The quantities to be discussed here are presented in Table 2-1. Their units, abbreviations of the quantities and units, and the legal standards for the quantities are also included. 

In 1955, R. A. Morton and associates in Liverpool announced the isolation of a quinone which they named ubiquinone for its ubiquitous occurrence.484 485 It was characterized as a derivative of benzoquinone attached to an unsaturated polyprenyl (isoprenoid) side chain (Fig. 15-24). In fact, there is a family of ubiquinones that from bacteria typically contains six prenyl units in its side chain, while most ubiquinones from mammalian mitochondria contain ten. Ubiquinone was also isolated by F. L. Crane and associates using isooctane extraction of mitochondria. These workers proposed that the new quinone, which they called coenzyme Q, might participate in electron transport. As is described in Chapter 18, this function has been fully established. Both the name ubiquinone and the abbreviation Q are in general use. A subscript indicates the number of prenyl units, e.g., Q10. Ubiquinones can be reversibly reduced to the hydro-quinone forms (Fig. 15-24), providing a basis for their function in electron transport within mitochondria and chloroplasts.486 490... 

Several terms used in vernacular science are not appropriate for scientific communication. The CIPM does not use such terms as parts per million, parts per billion, or parts per trillion or their abbreviations as expressions of quantities. The word weight is a force with the SI unit of newton, not a synonym for mass with the SI unit of kilogram. Terms for an object and quantities describing the object require a clear different action. Normality, molarity, and molal are obsolete terms no longer used. 

The d-f heteronuclear or lanthanide-transition metal (abbreviated as Ln-M) complexes attract interest from both academic and industry because of the challenge for their synthesis, the novelty of their structures, and their potential application as advanced materials, such as molecular or nano magnets,bimetallic catalysts, and sensors. The complexes can be assigned to three categories based on the nature of the Ln-M interaction (a) complexes with direct Ln-M bonding, (b) complexes with Ln-M interactions bridged by ligands, and (c) the complexes with ionically associated Ln-coordination units and M-coordination units. Most of the d-f heteronuclear complexes of carboxylic acids reported so far are found with type (b) structure, and very few of them are of structure type (c). The lanthanides and the transition metals in these complexes are far away from each other, and no direct Ln-M interactions have been observed. 

If it is known, the position of the substituent on the glucopyranose unit is indicated by a number preceding the substituent abbreviation. 6-SBEl-p-CD describes the monosubstituted sulfobutyl ether derivative with the substituent attached at one of the C-6 positions. More often than not, the substituent is introduced in a random reaction process such that introduction occurs with some defined distribution at the 2-, 3-, and/or 6-positions. For these preparations, no number precedes the substituent abbreviation. HP4-p-CD implies a tetra-substituted hydroxypropyl preparation with substituents randomly distributed over all three positions of the seven glucopyranose units. A number of common CDs and their nomenclature are given in Table 2. 

This paper attempts to point to some of the early and recent efforts for standardization in chemical nomenclature originating in the United States and gives general information concerning some of the objectives, procedures, and accomplishments. Nomenclature workers sometimes deal with symbols, forms, abbreviations, and pronunciation, and their work sometimes includes trade names. This paper is limited largely to work on the naming of chemical compounds and elements. 

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