Chapter XVIII: Our Relationship to the Atoms

I am sorry that this part of my story must remain incomplete for the present. I am not free to tell you all I know; you must try and get behind the scenes on your own account.

One thing I am at liberty to tell you is that my fellow-electrons who are locked up within the atoms are not without hope that they may gain their freedom once more at some future time. I know this first-hand, for I have met some fellow-electrons who have escaped from within an atom, but I shall delay telling you about these fellows till the succeeding chapter. My object in mentioning this fact now is to give you confidence in what I am about to say regarding the nature of the atom.

On one occasion I overheard a conversation between two men who were discussing the construction of matter. One remarked that the atoms were the bricks of the universe, whereupon the other asked how the little bricks were cemented together. I wish that man could have seen a lump of matter as we see it. He would have been surprised to learn that the atoms never really touch each other. They are always surging to and fro, or _vibrating_, and it is this motion which constitutes the _temperature_ of the body which they compose.

It must be clear, however, that in a solid body one atom attracts another atom across the intervening atomic spaces. This is another duty devolving upon us; what we do, really, is to upset the electric balance between the different atoms, and thus produce electrical attraction.

First of all, perhaps, I should explain that the different kinds of atoms are simply congregations of different numbers of electrons. Of course there is the other part, of which I am forbidden to speak--the part which man vaguely describes as _positive electricity_. However, you may take it from me that while it is true that the main difference between an atom of gold and an atom of iron, or of oxygen, is in the number of electrons it contains, there is a very important difference in the arrangement of the electrons. You know that they form rings outside one another, all of which revolve at enormous speeds. The number of electrons in the different rings varies according to the kind of atom.

It is quite correct for man to speak of the atoms containing certain definite numbers of electrons, but I should like you to understand clearly that the exact number of electrons is not permanently fixed; one or more electrons can slip off one atom and become attached to a neighbouring atom which happens to be capable of accepting it or them. It is the interchange of these few detachable electrons that causes one atom to attract another. In other words, it is the differently charged atoms which attract each other, just as man crowds a surplus of electrons on to one object and finds it attracted bodily towards another object having a deficiency of electrons.

It is this electrical attraction between the atoms which enables us to build up the particles, or _molecules_, of matter in such a variety of forms. First of all, we play the most important part within the atoms. We have formed only a limited number of such atoms. I am not free to tell you exactly how many, for man has discovered only about eighty of these different congregations of electrons, each kind of which he calls an _element_. The way in which we have coupled these different elementary atoms together must appear remarkable to all thinking men; there seems to be no end to the possible variety of combinations.

In one case we unite an atom of _chlorine_ to an atom of _sodium_ and thereby produce a molecule of common salt. In another case we unite an atom of _oxygen_ to two atoms of _hydrogen_, and the resulting combination is an invisible molecule of ordinary water.

It has always seemed to me very strange how some men have difficulty in regard to these combinations. I have heard a man ask how two different gases, hydrogen and oxygen, when united, should form a liquid, and not a gas. I wish you could see things as we see them. The atoms are neither gaseous, liquid, nor solid; they are little worlds of revolving electrons.

I have spoken of the attraction between atoms, and again between molecules, in forming a solid body. It will be clear that there is less of this _cohesive force_ in the case of a liquid, whereas it is absent entirely in the case of a gas. In this case the molecules have become so far separated from one another that they cease to attract each other, and if left free they will soon part company, and spread themselves broadcast over the face of the earth.

Whether a substance passes into a solid, a liquid, or a gaseous state, the atoms remain constant, but their vibratory motion is altered very considerably. However, I was about to tell you that we electrons can make some very interesting combinations of atoms. Those I have mentioned so far are of a very simple nature, but we have built up individual molecules containing hundreds of atoms. We link about a hundred atoms together and produce a molecule of what man calls _alum_, and we require to unite about a thousand atoms together to make one molecule of _albumen_ (the white of an egg).

When man speaks of a chemical change having taken place in a substance, it is simply the electrons who have made a friendly interchange of detachable electrons, thereby causing a different assemblage of the same atoms. During these changes we never alter the nature of the atom. That little world of revolving electrons known as an atom of gold, remains always an atom of gold. But you must not run away with the idea that the atoms will never change. Indeed, man has discovered that the atoms are not eternal, as I shall explain in the following chapter.

CHAPTER XIX

HOW WE MADE THE WORLD TALK

_THE SCRIBE'S NOTE ON CHAPTER NINETEEN_

The discovery of radium is within the memory of all.

Many exaggerated statements went abroad at the outset, but the
real facts are full of interest, and they have shed much new
light on many subjects.

Three different kinds of radiation were found to be emitted by
radium.

At first man could not tell what these were, so he named them
after the first three letters of the Greek alphabet--Alpha,
Beta, and Gamma, rays.

The electron tells the interesting story of these rays, and
relates the experiences of some fellow-electrons who escaped
from within a radium atom.