The Romance of Modern Chemistry

NATURE’S BUILDING MATERIAL containing one atom A and one atom B, and another molecule CD, containing one atom C and one atom D, then a chemical reaction will take place resulting in the formation of two new molecules AC and BD, or possibly AD and BC. This way of picturing the constitution of matter enables us to explain the definite proportions in which elements are found to combine. Take the case of copper and oxygen, already mentioned. Chemists have come to the conclusion that the atom of copper is four times as heavy as the atom of oxygen. Now the simplest way in which combination could take place would be by one atom of copper joining with one atom of oxygen, to form one particle or molecule, as it is called, of copper oxide. Each molecule, therefore, of copper oxide would contain four parts by weight of copper to one part of oxygen, or, what is the same thing, eight parts by weight of copper to two parts of oxygen. And what has been said of each separate molecule may be said also of the mass of copper oxide, which is simply the sum total of the myriad separate molecules. The proportion of copper to oxygen in the mass of copper oxide would be the same as in each individual molecule. Remembering that the atoms are indivisible, we can easily see that the next simplest ways in which copper could combine with oxygen would be by two atoms of copper joining with one atom of oxygen, or by one atom of copper joining with two atoms of oxygen. The atom of copper being four times as heavy as the atom of oxygen, the first of these two compounds would contain eight parts by weight of copper to one part of oxygen, while the second would contain eight parts by weight of copper to four parts of oxygen. As mentioned above, one of these 37