Atomic theory of Democritus

In antiquity, problems relating to chemistry were approached by two philosophies held to be mutually exclusive. The compositional view is best illustrated by the four elements as developed by Aristotle. The opposing view of structure, represented by the atomic theory of Democritus, lost out in antiquity because its materialism left no room for the spiritual. The so-... 

Epicurus (342-270 B.C.), revived the atomic theory of Democritus, though the efforts of his school to expound or develop it, appear not to have been very successful. Their theory is expounded very fully by the Latin poet Lucretius in his Be Rerum Natura. Indeed it is said that it was this work that inspired Gassendi in the seventeenth century to revive the Democritan atomic theory as part of his campaign against the authority of the Aristotelian philosophy of nature. 

In 1808, the English chemist John Dalton (1766-1844) published A New System of Chemical Philosophy, in which he revived the atomic theory of Democritus and showed that then-current knowledge in chemistry was consistent with the theory that matter is composed of atoms. Although atoms are too small to be seen by the naked eye—or even by optical microscopes—atomic theory came to be accepted during the 19th century as the best explanation for the fundamental composition of matter. In recognition of his contributions, Dalton is often referred to as the father of modern atomic theory. ... 

The atomic theory of Democritus was pure speculation and was much too general to be useful. Dalton s atomic theory, however, was a hypothesis that explained many facts in a simple and reasonable way. 

FIGURE 9.6 John Dalton (1766-1844). In 1803, Dalton restated the atomic theory of Democritus (fourth century b.c.) in a more modern form that with only slight modification is still considered valid today. In his honor, another name for an atomic mass unit is the dalton. Also in his honor, because he was the first person to write a description of color blindness, this affliction is sometimes referred to as daltonism. The original records of his experiments were destroyed by bombing in World War 11. 

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. 

Pyle, Andrew (1995), Atomism and Its Critics Problem Areas Associated with the Development of the Atomic Theory of Matter from Democritus to Newton, Thoemmes Press Bristol. 

To Leucippus and Democritus the Greeks and the Western world are indebted for the first clearly defined atomic theory of matter. Leucippus was the teacher of Democritus,... 

Probably the concept of atomism could have gone little further than with Democritus so long as exact experimental means of questioning nature were not employed. The atomic theory of matter and indeed the effort to account for the phenomena of nature by physical causes were to lose in interest to the ancient philosophers through the influence of the two greatest philosophers of ancient times, Plato and Aristotle. 

Democritus, 460-370 B.C., was a philosopher who proposed that the world is made up of empty space and tiny particles called atoms. Democritus thought that atoms are the smallest particles of matter and that different types of atoms exist for every type of matter. The idea that matter is made up of fundamental particles called atoms is known as the atomic theory of matter. 

In the course of spelling out the problem which the theory of substance should address, Aristotle considers various theories of his predecessors. The atomic theory of Leucippus and Democritus is singled out as of particular merit ... 

In chemistry, perhaps because of the significance in visualizing molecular strac-ture, there has been a focus on how students perceive three-dimensional objects from a two-dimensional representation and how students mentally manipulate rotated, reflected and inverted objects (Stieff, 2007 Tuckey Selvaratnam, 1993). Although these visualization skills are very important in chemistry, it is evident that they are not the only ones needed in school chemistry (Mathewson, 1999). For example, conceptual understanding of nature of different types of chemical bonding, atomic theory in terms of the Democritus particle model and the Bohr model, and... 

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. 

Interestingly, the teachings of Democritus (460-37Ibc) did not become so important, although in the sense of natural science (as we now know it), they were much more relevant. Leucippus was Democritus s teacher, and thus the scholar took over the basic ideas of atomic theory from his teacher atoms as tiny particles, too tiny to be visible, which were everlasting and could not be destroyed. They were supposedly made from the same material, but were of different sizes and weights. According to Democritus, life arises from a process in which the small particles of the moist earth combine with the atoms of fire. 

The first modern atomic theory was developed by John Dalton and first presented in 1808. Dalton used the term atom (first used by Democritus) to describe the tiny, indivisible particles of an element. Dalton also thought that atoms of an element are the same and atoms of different elements are different. In 1897, J. J. Thompson discovered the existence of the first subatomic particle, the electron, by using magnetic and electric fields. In 1909, Robert Millikan measured the charge on the electron in his oil drop experiment (electron charge = -1.6022 x 10-19 coulombs), and from that he calculated the mass of the electron. 

The atomic theory is so rooted in today s science that we readily accept the existence of atoms. Even though few of us have observed them directly, we have faith that everything around us is made of them. Yet we continue to probe the structure of the atom. It is interesting that we continue to seek greater knowledge about the atom and its smallest constituents in order to understand the largest entity we can think of— the universe. Just as Democritus quest was to build a philosophical system to explain nature, we continue to probe the atom in hope of understanding the universe and our place in it. 

In the light of modern criticism of scholars of early chemistry, we may be justified in disagreeing with Pliny that the magical and mystical writings attributed to Democritus of Abdera are by that same philosopher whose notions of the atomic structure of matter and of other problems of natural forces have given him a place in the history of chemical theory. 

The first name which appears to represent a chemical expert whose writings have been preserved fragmentarily in quotations or copies by later writers, is that of Democritus. This person is generally called by alchemical writers Democritus of Abdera, the philosopher who first enunciated an atomic theory. Internal and external evidence, however, make it clear that Democritus, the alchemist, has little in common with the philosopher of Abdera, and that this psuedo-Democritus lived at about the beginning of our era and belonged to the Alexandrian school of neoplatonists. The exact time of his life is unknown. H. Kopp10 considered that his work, Physica et Mystica, was written not earlier than the third century A.D. 

The atomic theory as originally conceived by Democritus and Epicurus, developed by Lucretius, and resurrected by Gassendi from about 1647 on, was doubtless the source from which Boyle derived his ideas on this subject, as he cites both Epicurus and Gassendi. Boyle, however, in the above proposition carefully avoids any dogmatic assertion of these hypotheses. It is plain, however, that these atoms or corpuscles as he calls them are a constant element of his thought. In part six (an appendix) to the Sceptical Chymist, he states more distinctly his definition of a chemical element. Carneades says 80... 

In 400 B.C., the Greeks explained that all matter was made of fire, earth, water, and air. A Greek philosopher, Democritus (460-370 B.C.), reasoned that matter was made of small, indivisible particles called atomos. Though the Greeks did not use experiments to test their ideas, the following scientists did, basing their atomic theories on experimental data ... 

Ancient philosophers in Greece, India, China, and Japan speculated that all matter was composed of four or five elements. The Greeks thought that these were fire, air, earth, and water. Indian philosophers and Aristotle from Greece also thought a fifth element—"aether" or "quintessence"—filled all of empty space. The Greek philosopher Democritus thought that matter was composed of indivisible and indestructible atoms. These concepts are now known as classical elements and classical atomic theory. 

In the past 200 years a great deal of experimental evidence has accumulated to support the atomic model. This theory has proved to be both extremely useful and physically reasonable. When atoms were first suggested by the Greek philosophers Democritus and Leucippus about 400 B.c., the concept was based mostly on intuition. In fact, for the following 20 centuries, no convincing experimental evidence was available to support the existence of atoms. The first real scientific data were gathered by Lavoisier and others from quantitative measurements of chemical reactions. The results of these stoichiometric experiments led John Dalton to propose the first systematic atomic theory. Dalton s theory, although crude, has stood the test of time extremely well. 

Although the Greek philosophers Democritus (460-370 Bc) and Epicurus (341-270 Bc) presented views of nature that included atoms, many hundreds of years passed before experimental studies could establish the quantitative relationships needed for a coherent atomic theory. In 1808, John Dalton published A New System of Chemical Philosophy in which he proposed that... 

While a fair amount of Democritus s ideas do not agree with modern atomic theory, his belief in the existence of atoms was amazingly ahead of his time. Despite this, his ideas did not turn out to be a major step toward our current understanding of matter. Over time, Democritus s ideas were met with criticism from other philosophers. What holds the atoms together they asked. Democritus could not answer the question. Other criticisms came from Aristotle (384-322 b.c.), one of the most influential Greek philosophers. Aristotle is shown in Figure 4-3. He rejected the atomic theory entirely... 

Although the concept of the atom was revived in the 18 century, it took the passing of another hundred years before significant progress was made. The work done in the 19 century by John Dalton (1766-1844), a schoolteacher in England, marks the beginning of the development of modern atomic theory. Dalton revived and revised Democritus s ideas based upon the results of scientific research he conducted. The main points of Dalton s atomic theory are shown in Figure 4-4. 

The advancements in science since Democritus s day served Dalton well, as he was able to perform experiments that allowed him to refine and verify his theories. Dalton studied numerous chemical reactions, making careful observations and measurements along the way. He was able to accurately determine the mass ratios of the elements involved in the reactions. Based on this research, he proposed his atomic theory in 1803. In many ways Democritus s and Dalton s theories are similar. What similarities and differences can you find between the two theories ... 

The concept of atoms is believed to have originated in ancient Greece. Democritus and his teacher Leppicutius were supporters of what has been called a discontinuous theory of matter, which means that all matter is made up of tiny particles, which are separated by spaces. They argued that if you kept cutting a sample of a substance up into smaller and smaller pieces, you would eventually get down to the smallest complete piece of that substance. Democritus called this smallest particle atomos, which means indivisible. 

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