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Chemistry for beginners

Chapter 9: THE ATOMIC THEORY
By Hereward Carrington
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Science - Chemistry/Biochemistry

About This Book

A concise introduction traces chemistry's development from ancient Greek and alchemical ideas through medieval practice to modern atomic theory and the periodic law. It explains elements, atomic weights, valency, analysis and synthesis, and differentiates organic and inorganic chemistry, including catalysis, enzymes, and hormones. Practical topics include spectroscopic methods, industrial chemistry, instruments, and ocean salinity. Later chapters address radioactivity, intra-atomic energy, electrons, astrophysical applications, and discussions on the origin of life and the philosophical implications connecting chemical theory with metaphysical questions.

THE ATOMIC THEORY

Here, then, we have at last the Atomic Theory—the theory, that is, that all matter, in all its stages, is built-up of extremely small particles which are so small, indeed, that they can no longer be sub-divided. They are the ultimate of matter—the “building stones of the Universe”—of which everything, animate and inanimate, is composed.

These atoms were held to be spherical in shape, of a certain definite weight and figure, according to the element or substance in question. Thus: “every particle of water is like every other particle of water, every particle of hydrogen is like every other particle of hydrogen, etc.” These ultimate particles—atoms—were held to be indestructible. These atoms all had their own particular weights, which might be denoted by number. Hence “atomic weight.”

These atoms, then, combine, forming molecules, or compounds of atoms; and molecules make up matter as we see and know it.

Further, most of the matter in the world is composed of a variety of elementary substances, limited in number. When more complex bodies are analyzed or broken-down, these elementary substances are always found. The number of those in Dalton’s day was unknown; but they had long been known as elements. Elements were, of course, composed of their own particular atoms; while all other substances were made-up of combinations of elements.