Atomic theory, proposal

Chemical analysis is an indispensable servant of modern technology whilst it partly depends on that modem technology for its operation. The two have in fact developed hand in hand. From the earliest days of quantitative chemistry in the latter part of the eighteenth century, chemical analysis has provided an important basis for chemical development. For example, the combustion studies of La Voisier and the atomic theory proposed by Dalton had their bases in quantitative analytical evidence. The transistor... 

Which one of the following atomic theories proposed by Dalton is wrong according to modern atomic theory ... 

In the early years of the nineteenth century, the new chemistry began to bear fruit on both sides of the Channel,270 as well as in other countries, notably in Sweden. The chemical atomic theory proposed by Dalton and developed by Berzelius led to the formulation of the stoichiometric laws of chemical combination and the diligent search for accurate atomic weights. The important link between atoms and electrical charges in the early years of the nineteenth century enabled a new interpretation of chemical combination and the theory of valency. Significant improvements in... 

Pasteur in Paris and was one of the pioneers of modern atomic theory, proposed the name phene . The word phene (from the Greek phainen , to shine) was proposed because benzene burns with a bright flame. Although it was not adopted for benzene, this word is now used in a number of names of arenes, such as phenol, phenanthrene, etc. 

Comparing and Contrasting Compare and contrast the atomic theories proposed by Democritus and John Dalton. 

Dalton s atomic theory proposed that matter is made up of indestructible atoms and that the atoms of an element are alike but differ from atoms of other elements. 

In the form of the atomic theory proposed by John Dalton in 1805, all atoms of a given element were thought to be identical. Chemists in the following decades set themselves the task of finding the relative masses of the atoms of the different elements by precise quantitative chemical analysis. Over a hundred years after Dalton s proposal was made, investigations with radioactive substances showed that not all atoms of a given element are identical. 

Dalton s atomic theory, proposed in about 1808, provided such a convincing explanation for the composition of compounds that it became generally accepted. Scientists came to believe that elements consist of atoms and that compounds are a specific collection of atoms bound together in some way. But what is an atom like It might be a tiny ball of matter that is the same throughout with no internal structure—like a ball bearing. Or the atom... 

Dalton s original atomic theory proposed that all atoms of a given element are identical. Did this turn out to be true after further experimentation was carried out Explain. 

John Dalton s atomic theory proposes that all matter is made up of tiny particles called atoms. His theory is described in Section 5.1. 

This proposal is called the atomic theory. As with any theory, its value depends upon its ability to aid us in explaining facts of nature. There is no more valuable theory in science than the atomic theory. We shall use it throughout this course. Later, in Chapter 14, we shall review many of the types of experiments which cause chemists to regard the atomic theory as the cornerstone of their science. 

At the beginning of this course you were a new tenant. You were told that chemists believe in atoms and you were asked to accept this proposal tentatively until you yourself knew the evidence for it. Since that time, we have used the atomic theory continuously in our discussions of chemical phenomena. The atomic theory passes the test of a good theory it is useful in explaining a large number of experimental observations. We have become convinced there are atoms. 

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 first plausible theory of the electronic structure of the atom was proposed in 1914 by Niels Bohr (1885-1962), a Danish physicist. In order to explain the hydrogen spectrum (Fig. 17-1), he suggested that in each hydrogen atom, the electron revolves about the nucleus in one of several possible circular orbits, each having a definite radius corresponding to a definite energy for the electron. An electron in the orbit closest to the nucleus should have the lowest energy. With the... 

Later, there were improvements in the thermal theories. Probably the most significant of these is the theory proposed by Zeldovich and Frank-Kamenetskii. Because their derivation was presented in detail by Semenov [4], it is commonly called the Semenov theory. These authors included the diffusion of molecules as well as heat, but did not include the diffusion of free radicals or atoms. As a result, their approach emphasized a thermal mechanism and was widely used in correlations of experimental flame velocities. As in the... 

Isotopes answer a puzzle that troubled chemists ever since Dalton proposed his atomic theory. Dalton said that the key property of an atom is not its size or shape but its weight. Each element is characterized by an atomic weight defined relative to that of hydrogen. The fact that these relative atomic weights were usually... 

None of the theories proposed before 1951 to explain the nature of the bonding in metal-olefin complexes was entirely satisfactory (35). Chatt (S3) suggested that, in addition to the ordinary coordinate bond, some sort of bond involving the filled d-orbitals of the metal atom was essential for coordination of the olefin, but such a bond was difficult to formulate until Dewar (64) described it in terms of molecular orbitals. The structure which he proposed for the silver-olefin complexes, and that subsequently proposed for the platinum-olefin complexes by Chatt and Duncanson (35) are shown schematically in structures (I) and (II). The type bond, which has also been called a ji-bond (64, 4), is formed by the overlap of the filled bonding... 

William B. Jensen begins the volume with an overview of scientific atomic theories from the 17 through 20 centuries. He mentions ancient atomism, but he begins in earnest analyzing corpuscular theories of matter proposed or entertained by natural philosophers in the 17 century. He describes the dominant flavors of atomic notions over fom centuries, from the mechanical through the dynamical, gravimetric, and kinetic, to the electrical. Jensen is Oesper Professor of Chemical Education and History of Chemistry at the University of Cincirmati and was the foimding editor of the Bulletin for the History of Chemistry. 

In the classical era in Europe, the theory and practice of chemistry were pursued mainly by the ancient Greeks, who made many important discoveries in metallurgy in particular and who are also credited with proposing the earliest version of the atomic theory. The Greek chemical tradition declined when mysticism displaced the observational approach in the second century of the Common Era, and subsequently was largely lost in Europe after the fall of Rome in 410 c.E. In the 11th. century c.E., the quasiscience of alchemy returned to Europe via the Arabs, who also introduced Persian, Indian, and Chinese influences. 

The chemist John Dalton (of atomic theory fame) was color-blind. He thought it probable that the vitreous humor of his eyes (the fluid that fills the eyeball behind the lens) was tinted blue, unlike the colorless fluid of normal eyes. He proposed that after his death, his eyes should be dissected and the color of the vitreous humor determined. His wish was honored. The day after Dalton s death in July 1844, Joseph Ransome dissected his eyes and found the vitreous humor to be perfectly colorless. Ransome, like many scientists, was reluctant to throw samples away. He placed Dalton s eyes in ajar of preservative (Fig. 1), where they stayed for a century and a half. 

---