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реферирование we meet idea of an element very early in our sturdy of chemistry. the ancients suspected that there must be some very simple substances from which more complicated were build. at one time they thought that everything might be made up of earth, air and water; these got the name “element” which comes from the same word as “elementary” or simple. this idea, though wrong, is still an important one. in the middle of the 17th century robert boyd recognized the modern type of an element. his idea was that an element was just something which could not be broken down chemically into anything simpler. he knew of metals like iron, cooper, tin, lead, gold and silver and nonmetals like carbon and sulphur, and some gases which were called “air”. in the years after boyle over one hundred different elements have been defined. some of these are quite common and well known but a lot of them are man made. examples are mendelevium, nobelium, and lawrencium. one of the first distinctions between elements was the division into metals and nonmetals. as you know, a dull red mercuric oxide is decomposed into mercury and oxygen. the weights of oxygen and mercury which are obtained are together equal to the weight of mercury oxide. similarly, water is decomposed by electrolyses into oxygen and hydrogen. no chemist, however, has been able to separate any other substances from mercury, oxygen or hydrogen: these three substances are known, therefore, as elements. an element is a substance which, so far as is known contains only one kind of atom. it has been found possible to resolve all known substances into about 109 elements: many of these elements are rare, and relatively few are common in nature. sugar, starch, cellulose, wood and paper, for example, differ from one another in many ways, yet each of these substances is composed of the same three elements: carbon, hydrogen and oxygen. just as several thousand bricks may be arranged to from many different types of buildings, so may the atoms o elements be arranged in different ways to from molecules of different types of matter. astronomers have found that the same element which are common on the earth, e.g. nitrogen, carbon and hydrogen, are also the commonest in the sun and other stars. thus elements are the primary building materials of the universe. текста онлайн,
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