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The atomic theory of matter

The vital breakthrough that allowed chemistry to become the central science was the demon­stration of the atomic nature of matter. In about 1800 John Dalton realized that all matter is composed of relatively few elements. He



Introduction 9

The white smokepouring from the engine exhausts of aerobatic aircraft consists of finely divided titanium diox­ide. This metallic compound also finds uses in electronic components and in paint and paper making. The preparation and properties of metals and their com­pounds are part of the study of inorganic chemistry.

Gummy resinseeping from the seed pods of opium poppies contains morphine and related com­pounds. They belong to a group of plant-produced chemicals known as alka­loids. Like most other drugs and physiologically active substances, alkaloids are dealt with in organic chem­istry.

postulated that these elements combine to­gether in accordance with their valency to make up discrete molecules. (Thus, water, H20, is formed by the combination of two hy­drogen atoms with one oxygen atom.) Antoine Lavoisier proved that burning is simply the chemical combination of the combustible ma­terial with the oxygen of the air. In the early nineteenth century, Friedrich Wohler synthe­sized urea from inorganic materials and dem­onstrated that there is no difference in princi­ple between inanimate substances and those of living matter.

The atomic theory allows us to treat all the properties of matter in terms of the molecules that make it up. This has enabled the develop­ment of chemistry (and physics) to progress rapidly. An explanation in terms of molecular structure allows scientists to carry out rational experiments to test the explanations. Further­more, correct explanations of significant and desired properties lead to the possibility of predicting improvements to those properties by molecular modification. This, in turn, then allows additional experiments to produce ma­terials with such improved properties.

This chain of events is the basis of all ap­plied research, and the chief reason why living standards have so improved that in the devel­oped nations the good life should now be possible for everyone.


Date: 2015-12-11; view: 74

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