Matter atomic theory

Classification of matter, atomic theory, inside the atom 2.1-2.4... 

Historically, one of the key examples of this is the evaluation hy Einstein of the significance of Brownian motion, which led to the substantiation of the ideas behind the atomic theory of matter. Atomic theory was under challenge at the time from well-established and prestigious names within the scientific community. The phenomenon of Brownian motion and its interpretation was one major factor in the acceptance of the theory. Yet this acceptance involved interpretation of the unseen atomic world - the motion of sub-microscopic atoms and molecules - in terms of the motion of the seen world - the motion of smoke or dust particles under the microscope. 

The concept that all substances are composed of elements and atoms goes back at least 2000 years. Originally, only four elements were recognized air, earth, fire, and water. Each substance was thought to consist of very small particles, called atoms, that could not be subdivided any further. This early mental concept of the nature of matter was extremely prescient, considering there were no experimental results to indicate that matter should be so and none to verify that it was so. Modern atomic theory is much more rigorously based, and we even have the ability to see atoms with special tunneling microscopes. All of chemistry is based on how atoms react with each other. 

Urstoff, m. primary matter (formerly) ele ment initial material, -lehre,/. the theory of a primary matter of which the elements are composed atomism, atomic theory. 

In 1808, an English scientist and schoolteacher, John Dalton, developed the atomic model of matter that underlies modem chemistry. Three of the main postulates of modem atomic theory, all of which Dalton suggested in a somewhat different form, are stated below and illustrated in Figure 2.1. 

Thus we see that the properties of gases provide a substantial basis for developing the atomic theory. The gaseous state is, in many ways, the simplest state of matter for us to understand. The regularities we discover are susceptible to detailed mathematical interpretation. We shall examine these regularities in this chapter. We shall find that their interpretation, called the kinetic theory, provides an understanding of the meaning of temperature on the molecular level. 

This success of the atomic theory is not surprising to a historian of science. The atomic theory was first deduced from the laws of chemical composition. In the first decade of the nineteenth century, an English scientist named John Dalton wondered why chemical compounds display such simple weight relations. He proposed that perhaps each element consists of discrete particles and perhaps each compound is composed of molecules that can be formed only by a unique combination of these particles. Suddenly many facts of chemistry became understandable in terms of this proposal. The continued success of the atomic theory in correlating a multitude of new observations accounts for its survival. Today, many other types of evidence can be cited to support the atomic postulate, but the laws of chemical composition still provide the cornerstone for our belief in this theory of the structure of matter. 

The initial set of experiments and the first few textbook chapters lay down a foundation for the course. The elements of scientific activity are immediately displayed, including the role of uncertainty. The atomic theory, the nature of matter in its various phases, and the mole concept are developed. Then an extended section of the course is devoted to the extraction of important chemical principles from relevant laboratory experience. The principles considered include energy, rate and equilibrium characteristics of chemical reactions, chemical periodicity, and chemical bonding in gases, liquids, and solids. The course concludes with several chapters of descriptive chemistry in which the applicability and worth of the chemical principles developed earlier are seen again and again. 

With remarkable accuracy, Democritus in the fifth century B.C. set the stage for modem chemistry. His atomic theory of matter, which he formulated without experimental verification, still stands, more or less intact, and encapsulates the profound truth that nature s stunning wealth boils down to atoms and molecules. As science uncovers the mysteries of the world around us, we stand ever more in awe of nature s ingenious molecular designs and biological systems nucleic acids, saccharides, proteins, and secondary metabolites are four classes of wondrous molecules that nature synthesizes with remarkable ease, and uses with admirable precision in the assembly and function of living systems. 

The relation between matter and ether was rendered clearer by Lord Kelvin s vortex-atom theory, which assumed that material atoms are vortex rings in the ether. The properties of electrical and magnetic systems have been included by regarding the atom as a structure of electrons, and an electron as a nucleus of permanent strain in the ether— a place at which the continuity of the medium has been broken and cemented together again without fitting the parts, so that there is a residual strain all round the place (Larmor). 

It may be remarked that there is no call for an atomic theory of energy, analogous to the atomic theories of matter and electricity, as the discontinuity arises from the peculiar character of the system (cf. Planck, 45, 5, 1912). 

Study, the students are taught the basic concepts of chemistry such as the kinetic theory of matter, atomic stmcture, chemical bonding, stoichiometry and chemical calculations, kinetics, energetics, oxidation-reduction, electrochemistry, as well as introductory inorgarric and organic chemistry. They also acquire basic laboratory skills as they carry out simple experiments on rates of reaction and heat of reaction, as well as volrrmetric analysis and qualitative analysis in their laboratory sessions. 

The sub-micro level is real, but is not visible and so it can be difficult to comprehend. As Kozma and Russell (1997) point out, understanding chemistry relies on making sense of the invisible and the untouchable (p. 949). Explaining chemical reactions demands that a mental picture is developed to represent the sub-micro particles in the substances being observed. Chemical diagrams are one form of representation that contributes to a mental model. It is not yet possible to see how the atoms interact, thus the chemist relies on the atomic theory of matter on which the sub-micro level is based. This is presented diagrammatically in Fig. 8.2. The links from the sub-micro level to the theory and representational level is shown with the dotted line. 

Johnstone (2000) emphasises the importance of beginning with the macro and symbolic levels (Fig. 8.3) because both comers of the triangle are vistrahsable and can be made concrete with models (p. 12). The strb-micro level, by far the most difficult (Nelson, 2002), is described by the atomic theory of matter, in terms of particles such as electrorrs, atoms and molecules. It is commorrly referred to as the molecular level. Johnstone (2000) describes this level simirltaneorrsly as the strength and weakness of the subject of cherrristry it provides strength through the intellectual basis for chemical explanatiorrs, but it also presents a weakness when novice students try to learn and rmderstand it. 

In this chapter, we present the atomic perspective of matter, as expressed by atomic theory and the principies of atomic stmcture. We describe the buiiding biocks of atoms eiectrons, protons, and neutrons. Then we show how these interact to form aii the chemicai eiements and expiain which combinations are stabie. Next we describe how atomic masses are reiated to these buiiding biocks. We end the chapter by introducing ions, atoms that have either iost or gained eiectrons. Eurther appiications of radioactive atoms in medicine are found within the chapter. 

Chemistry is a quantitative science, and chemists frequentiy measure amounts of matter. As the atomic theory states, matter consists of atoms, so measuring amounts means measuring numbers of atoms. Counting atoms is difficuit, but we can easiiy measure the mass of a sampie of matter. To convert a mass measurement into a statement about the number of atoms in a sampie, we must know the mass of an individuai atom. 

Matter possesses mass, and matter is made up of atoms, so atoms possess mass. This property was already recognized in the time of John Dalton, who made it one of the postulates of his atomic theory. 

Alchemical thinking helped lead the Society to interpret the implications of modem atomic theory in a way that emphasized the unity of matter (and even of energy) that saw oneness, rather than disunity and distinctness, as a major substratum of atomic theory and that pushed to spiritualize this principle. This grasping for ever simpler and more basic unity is, of course, not so uncommon an impulse in twentieth-century physics. (Consider unified field theories, and even the Theory of Everything in more recent physics.) Alchemy allowed the scientists and Hermeticists of the Alchemical Society to re-enchant science by positing the origins of the modem scientific push for unity in ancient Hermetic spirituality. 

At the end of the nineteenth century chemistry was at the cutting edge as a theoretically well-founded experimental science. The most advanced and controversial physical theories of the day had their origin in chemical research, which concerned itself with all aspects related to the nature and constitution of matter. The theories of electrons (sic), atoms and molecules were the working models of practising chemists. Optical activity, like other forms of spectroscopy in its infancy, was the pursuit of analytical chemistry. 

Such was the alchemistic view of the generation of the metals a theory which is admittedly cmde, but which, nevertheless, contains the germ of a great principle of the utmost importance, namely, the idea that all the varying forms of matter are evolved from some one primordial stuff — a principle of which chemical science lost sight for awhile, for its validity was unrecognised by Dalton s Atomic Theory (at least, as enunciated by him). 

At the beginning of the nineteenth century, John Dalton (see plate 15 (sic should be 16 ) put forward his Atomic Theory in explanation of these facts. This theory assumes (1) that all matter is made up of small indivisible and indestructible particles, called "atoms" (2) that all atoms are not alike, there being as many different sorts of atoms as there are elements (3) that the atoms constituting any one element are exactly alike and are of definite weight and (4) that compounds are produced by the combination of different atoms. Now, it is at once evident that if matter be so constituted, the stoichiometric laws must necessarily follow. For the smallest particle of any definite compound (now called a "molecule") must consist of a definite assemblage of different atoms, and these... 

Toward the close of the nineteenth century, chemists had two invaluable conceptual tools to aid them in their understanding of matter. The first was John Dalton s atomic theory, which you have studied intensively in previous chemistry courses. Dalton s atomic theory, first published in 1809, provided chemists with a framework for describing and explaining the behaviour of matter during chemical reactions. As you can see in Figure 3.1, the model of the atom that resulted from this theory was very simple. 

As you know, Dalton s atomic theory no longer applies in its original form, and Mendeleev s periodic table has undergone many changes. For example, scientists later discovered that atoms are not the most basic unit of matter because they are divisible. As well, the modern periodic table lists the elements in order of their atomic number, not their atomic mass. Of course, it also includes elements that had not been discovered in Mendeleev s time. Even so, in modified form, both of these inventions are still studied and used today in every chemistry course around the world. 

Chemists needed Dalton s atomic theory to advance their understanding of matter and its behaviour during chemical reactions. His atomic model, however, was inadequate for explaining the behaviour of substances. 

According to E. Stroker [1], it was not the Democritean atomistic theory of matter which was the precursor of the modem Daltonian atomic theory, as generally accepted, but the Aristotelian concept of minima naturalia, developed in the Middle Age. 

Dalton s atomic theory chem Theory forming the basis of accepted modern atomic theory, according to which matter is made of particles called atoms, reactions must take place between atoms or groups of atoms, and atoms of the same element are all alike but differ from atoms of another element. dol tonz 3,tam-ik the-o-re ... 

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