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In chemistry, the history of molecular theory traces the origins of the concept or idea of the existence of strong chemical bonds between two or more atoms. The modern concept of molecules can be traced back towards pre-scientific Greek philosophers such as Leucippus who argued that all the universe is composed of atoms and voids. Circa 450 BC Empedocles imagined fundamental elements (fire (20px), earth (20px), air (20px), and water (20px)) and "forces" of attraction and repulsion allowing the elements to interact. Prior to this, Heraclitus had claimed that fire or change was fundamental to our existence, created through the combination of opposite properties. In the Timaeus, Plato, following Pythagoras, considered mathematical entities such as number, point, line and triangle as the fundamental building blocks or elements of this ephemeral world, and considered the four elements of fire, air, water and earth as states of substances through which the true mathematical principles or elements would pass. A fifth element, the incorruptible quintessence aether, was considered to be the fundamental building block of the heavenly bodies. The viewpoint of Leucippus and Empedocles, along with the aether, was accepted by Aristotle and passed to medieval and renaissance Europe. A modern conceptualization of molecules began to develop in the 19th century along with experimental evidence for pure chemical elements and how individual atoms of different chemical substances such as hydrogen and oxygen can combine to form chemically stable molecules such as water molecules. ==17th century== The earliest views on the shapes and connectivity of atoms was that proposed by Leucippus, Democritus, and Epicurus who reasoned that the solidness of the material corresponded to the shape of the atoms involved. Thus, iron atoms are solid and strong with hooks that lock them into a solid; water atoms are smooth and slippery; salt atoms, because of their taste, are sharp and pointed; and air atoms are light and whirling, pervading all other materials. It was Democritus that was the main proponent of this view. Using analogies based on the experiences of the senses, he gave a picture or an image of an atom in which atoms were distinguished from each other by their shape, their size, and the arrangement of their parts. Moreover, connections were explained by material links in which single atoms were supplied with attachments: some with hooks and eyes others with balls and sockets (see diagram).〔See ''testimonia'' DK 68 A 80, DK 68 A 37 and DK 68 A 43. See also 〕 With the rise of scholasticism and the decline of the Roman Empire, the atomic theory was abandoned for many ages in favor of the various four element theories and later alchemical theories. The 17th century, however, saw a resurgence in the atomic theory primarily through the works of Gassendi, and Newton. Among other scientists of that time Gassendi deeply studied ancient history, wrote major works about Epicurus natural philosophy and was a persuasive propagandist of it. He reasoned that to account for the size and shape of atoms moving in a void could account for the properties of matter. Heat was due to small, round atoms; cold, to pyramidal atoms with sharp points, which accounted for the pricking sensation of severe cold; and solids were held together by interlacing hooks. Newton, though he acknowledged the various atom attachment theories in vogue at the time, i.e. “hooked atoms”, “glued atoms” (bodies at rest), and the “stick together by conspiring motions” theory, rather believed, as famously stated in "Query 31" of his 1704 ''Opticks'', that particles attract one another by some force, which “in immediate contact is extremely strong, at small distances performs the chemical operations, and reaches not far from particles with any sensible effect.” 〔(a) Isaac Newton, (1704). Opticks. (pg. 389). New York: Dover. (b) 〕 In a more concrete manner, however, the concept of aggregates or units of bonded atoms, i.e. "molecules", traces its origins to Robert Boyle's 1661 hypothesis, in his famous treatise ''The Sceptical Chymist'', that matter is composed of ''clusters of particles'' and that chemical change results from the rearrangement of the clusters. Boyle argued that matter's basic elements consisted of various sorts and sizes of particles, called "corpuscles", which were capable of arranging themselves into groups. In 1680, using the corpuscular theory as a basis, French chemist Nicolas Lemery stipulated that the acidity of any substance consisted in its pointed particles, while alkalis were endowed with pores of various sizes.〔Lemery, Nicolas. (1680). An Appendix to a Course of Chymistry. London, pgs 14-15.〕 A molecule, according to this view, consisted of corpuscles united through a geometric locking of points and pores. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「History of molecular theory」の詳細全文を読む スポンサード リンク
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