Chemistry is the science which treats of the nature, laws of combination, and mutual actions of the minute particles of the different sorts of matter composing our universe, and the properties of the compounds they form. It is a modern science developed from the earlier Alchemy.
The alchemists in their study of minerals and metallic ores made important but isolated discoveries, and at the close of the 17th century the German chemist Becher threw out certain speculations regarding the cause of combustion, which were taken up and extended by Stahl in the 'phlogistic theory', and constitute the first generalization of the phenomena of chemistry, though the theory itself was diametrically opposed to the truth. About the middle of the 18th century Dr. Black made his great discovery of a gas differing from atmospheric air, rapidly followed by that of a number of other gases by Cavendish, Rutherford, Priestley, Scheele, etc; and the discovery of oxygen by the two last-named chemists afforded to Lavoisier the means of revolutionizing and systematizing the science. By a series of experiments he showed that all substances, when burned, absorb oxygen, and that the weight of the products of combustion is exactly equal to that of the combustible consumed and of the oxygen which has disappeared. The application of this theory to the great majority of the most important chemical phenomena was obvious and the Stahlian hypothesis disappeared.
A yet more important step was the discovery by Dalton of the laws of chemical combination. His theory was immediately taken up by Berzelius, to whose influence, and careful determination of the chemical equivalents of almost all the elements then known, its rapid adoption was mainly due. To Berzelius we owe many of the modern improvements in the methods of analysis, while Sir Humphry Davy laid the foundation of electro-chemistry.
From the 19th century every branch of the science was advanced, but the most extraordinary progress was made in organic chemistry, or the chemistry of the carbon compounds, and in physical chemistry, a branch of chemistry which is closely allied to certain branches of physics.
The investigations of chemists showed that the great majority of the different natural substances can be broken up into substances of less complicated nature, which resist all further attempts to decompose them, and appear to consist of only one kind of matter. These substances, by union of which all the different sorts of known matter are built up, are called the chemical elements. The list includes such substances as gold, iron, oxygen, hydrogen, carbon, calcium, etc. When any two or more of these elements are brought in contact, under suitable conditions, they may unite and form chemical compounds of greater or less complexity, in which the constituents are held in union by a form of energy which has received the name of chemical affinity. This affinity is characterized by its acting between dissimilar particles, and producing a new kind of matter, readily distinguishable from either of the substances combining to form it, and which cannot be again separated into its elements by merely mechanical processes. In these respects, and also in the fact that union occurs in definite proportions by weight, the compounds differ from mere mixtures of elements.
Around 1900, about eighty elements had been identified. During the 20th century many more were discovered, and by 2008 118 elements were known, though elements with larger atomic numbers than 92 do not occur naturally, rather they have all been produced artificially by bombarding other elements with particles. Elements are usually grouped by their number of protons, and represented in a table known as the periodic table, in which hydrogen is numbered 1, oxygen is numbered 8 and iron is numbered 26. Research Chemistry
Abbreviations
SciTech
Research Chemistry