Indivisible

For two thousand years atoms were considered the smallest and indivisible units of nature. At the beginning of the nineteenth century Dalton got chemistry on the path of atomic theory with his book, A New System of Chemical Philosophy, in which he argued that unbreakable atoms form compounds by linking with other atoms in simple... 

Many elements are familiar to us in everyday life. Iron is an element used for making ships, cars, spades, etc. There are about 90 such familiar elements, including helium, oxygen, nitrogen, mercury, platinum, and gold. As an element, iron consists of atoms of iron, the smallest building blocks, each of which is indivisible by chemical means. A lump of iron comprises millions, trillions, and zillions of atoms, and the mass of each atom of iron is very small, about 10 g In a piece of iron weighing 50 g, there are about lO atoms. 

The notion of an atomic operation is important for synchronization. An atomic operation is one that is indivisible. Once initiated, it will continue to completion. There are usually a large number of synchronization primitives in a parallel computer, most commonly test and set primitives, or semaphores implemented in hardware (10). A test and set operation tests the current value of a variable and optionally sets a new value, all in one indivisible operation. 

Racemic and Mesotartaric Acids.—These two acids represent two inactive types of compounds containing a< yminct7 ic carbon atoms (see above). Apart from certain well-marked differences in physical properties they also differ in one important feature racemic acid can be lesoh-ed into its optical enantiomorphs, whereas mesotartaric acid cannot. The latter belongs to what is termed the inactive indivisible type. If we examine the structuial formula of tartaric acid it will l>e seen that it possesses two asyimnetric carbon atoms, denoted in the formula by thick type. 

Unteilbarkeit, /. indivisibility, unteilhaftig, a. not sharing, nonparticipating, unten, adt. below, beneath, underneath, at the bottom. 

The chemical formula for water shows how formulas are constructed. The formula lists the symbols of all elements found in the compound, in this case H (hydrogen) and O (oxygen). A subscript number after an element s symbol denotes how many atoms of that element are present in the molecule. The subscript 2 in the formula for water indicates that each molecule contains two hydrogen atoms. No subscript is used when only one atom is present, as is the case for the oxygen atom in a water molecule. Atoms are indivisible, so molecules always contain whole numbers of atoms. Consequently, the subscripts in chemical formulas of molecular substances are always integers. We explore chemical formulas in greater detail in Chapter 3. 

All matter is composed of tiny, indivisible particles called atoms. 

Like Democritus, Dalton got much right. But the concept of atoms as indivisible particles would soon be overthrown. 

Work by other scientists showed that cathode ray particles were indeed much smaller than hydrogen. This led Thomson to an astounding conclusion. Cathode rays must be a part of an atom, he announced to the world in 1897. This was big news. All atomic theories before this one, going back to Democritus, held that the atom was indivisible. Now, here was J.J. Thomson saying it was made up of even smaller particles. These particles were soon named electrons. 

Chemists were not able to use their methods to determine the structure of the atom. The discovery of radioactivity by Henri Becquerel and the work of Marie and Pierre Curie showed, however, that heavy elements were not stable. The earlier postulate of their indivisibility could no longer be maintained. In 1906 Ernest Rutherford made the next horrorif-ic revelation his scattering experiments showed that the atom was almost empty. A tiny nuclear mass was circled by electrons at a large distance. For comparison, if the nucleus were the size of a cherry pit and were placed in the center of a football field, the electrons would be circulating in the back rows of the stadium. If the nucleus were the size of a football, the first electrons would be circling it at a distance of one kilometer. Between them would be absolute emptiness. 

Sir Ernest Rutherford (1871-1937 Nobel Prize for chemistry 1908, which as a physicist he puzzled over) was a brilliant experimentalist endowed with an equal genius of being able to interpret the results. He recognized three types of radiation (alpha, beta, and gamma). He used scattering experiments with alpha radiation, which consists of helium nuclei, to prove that the atom is almost empty. The diameter of the atomic nucleus is about 10 000 times smaller than the atom itself. Furthermore, he proved that atoms are not indivisible and that in addition to protons, there must also be neutrons present in their nucleus. With Niels Bohr he developed the core-shell model of the atom. 

Elements are composed of indivisible particles, called atoms. 

From 50 years to 100 years after Dalton proposed his theory, various discoveries showed that the atom is not indivisible, but really is composed of parts. Natural radioactivity and the interaction of electricity with matter are two different types of evidence for this subatomic structure. The most important subatomic particles are listed in Table 3-2, along with their most important properties. The protons and neutrons occur in a very tiny nucleus (plural, nuclei). The electrons occur outside the nucleus. 

Schaffner, K. F. (1998), Genes, behavior and developmental emergentism one process, indivisible Model organisms and behavioral genetics a rejoinder , Philos. Sci, 65, 209-252 276-288. 

There is a long-standing habit in the health economics literature of supporting the need to regulate health care services in market failures such as information asymmetries, complexity and uncertainty, indivisibilities and externalities. These imperfections are also present in the market of a resource that is very important in the health service production process pharmaceutical products. However, the pharmaceutical market also presents certain specific characteristics that are of particular importance and have been used as arguments in favour of the need to adopt public policies of price intervention and regulation. 

Modern alchemy s claims that atoms were not indivisible and immutable and that humans could effect elemental transmutation entailed a rethinking of the nature of money during a moment of economic and monetary crisis. 

According to the Oxford English Dictionary, the word molecule seems to have arisen in the seventeenth century in the discussions initiated by the physical speculations of Descartes. Early formal definitions described a molecule as a group of atoms mechanically indivisible (H. E. Roscoe, Elementary Chemistry [1871], p. 169) or a group of atoms drawn and held together by what chemists call affinity (J. Tyndall, Longm. Mag. 1 [1882], 30). 

Determine a consistent level of abstraction in relation to actions Are you going to worry about individual keystrokes or talk only about broad transactions The highest-level action that could be useful should accomplish a business task or objective or should abstract a group of such actions. The lowest-level action that could be useful should constitute an indivisible interaction if the interaction fails to complete successfully or otherwise is aborted, there should be no effect that would be useful at the business level. 

Several strands of evidence came together at the beginning of the twentieth century to suggest that the atom, originally envisaged by the Greek philosophers as the smallest indivisible unit of matter, was, in fact, composed of smaller particles, subsequently named protons, neutrons, and electrons. The story begins in the nineteenth century with efforts to identify the atom itself, followed by research which led to the identification of the... 

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