Part 1 (2/2)

We haven't seeet very far yet toward radio but you can see hoe shall when I tell you that next tiames such as are played in the atoms of copper which form the wires of radio sets and of how these wires can do e call ”carrying an electric current”

LETTER 2

WHY A COPPER WIRE WILL CONDUCT ELECTRICITY

MY DEAR YOUNG ATOMIST:

You have learned that the siroup which can be formed by protons and electrons is one proton and one electron chasing each other around in a fast gaen A ether

All the other possible kinds of groups are more complicated The next sias of which small quantities are obtained from certain oil wells and there isn't very as, as we call it, because it won't burn or co else It doesn't care to enter into the larger garoups It is satisfied to be as it is, so that it isn'telse out of it That's the reason why it is so highly reco balloons or airshi+ps, because it cannot burn or explode It is not as light as hydrogen but it serves quite well forballoons buoyant in air

This heliuht at the center there is a sroup which contains all the protons and two of the electrons The other two electrons play around quite a little way froroup It will roup ”the nucleus” of the atom

It is the center of the atom and the other two electrons play around about it just as the earth and Mars and the other planets play or revolve about the sun as a center That is e shall call these two electrons ”planetary electrons”

There are about ninety different kinds of atoms and they all have naen and helium For example, there is the iron atom, the copper atom, the sulphur atoht to know and so, before telling you oing to write down the names of some of the atoms which we have in the earth and rocks of our world, in the water of the oceans, and in the air above

Start first with air It is a as is a different kind of atoen and a very sases which I won't bother you with learning Most of the air, however, is nitrogen, about 78 percent in fact and alen so that all the gases other than these two make up only about 12 percent of the atmosphere in which we live

[Illustration: Pl II--Bird's-eye View of Radio Central (Courtesy of Radio Corporation of Areat deal of oxygen; about 473 percent of the atoen atoms About half of the rest of the atoms are of a kind called silicon Sand is en and you kno much sand there is

About 277 percent of the earth and its rocks is silicon The next most important kind of atom in the earth is aluminum and after that iron and then calciues: Aluminum 78 percent; iron 45 percent; calcium 35 percent; sodiunesium 22 percent Besides these which are en and the same amount of carbon Then there is a little phosphorus, a little sulphur, a little fluorine, and small amounts of all of the rest of the different kinds of atoen, about 858 percent of oxygen and 107 percent of hydrogen That is what you would expect for water is made up of en and one atoen atoen atoen atoen in water there are about eight pounds of oxygen That is why there is about eight tien in sea water as there is of hydrogen

Most of sea water, therefore, is just water, that is, pure water But it contains some other substances as well and the best known of these is salt Salt is a substance the molecules of which contain atoms of sodium and of chlorine That is why sea water is about 11 percent sodium and about 21 percent chlorine There are some other kinds of atoets all the substances which the waters of the earth dissolve and carry down to it but they are uni about the naain the question of how they are formed by protons and electrons Noays have a nucleus or center and so around that nucleus like tiny planets The only differences between one kind of atom and any other kind are differences in the nucleus and differences in the nue about the nucleus

Nothere is always in it just as many electrons as protons For example, the iron ato around it The copper atom has twenty-nine electrons as tiny planets to its nucleus What does that mean about its nucleus? That there are twenty-nine more protons in the nucleus than there are electrons Silver has even more planetary electrons, for it has 47 Radium has 88 and the heaviest atoht use numbers for the different kinds of atoms instead of names if anted to do so We could describe any kind of ato how en would be number 1, helium number 2, lithium of which you perhaps never heard, would be nuen is 8, sodium is 11, chlorine is 17, iron 26, and copper 29 For each kind of atom there is a number Let's call that number its atomic number

Now let's see what the atomic number tells us Take copper, for example, which is nu around the nucleus The nucleus itself is a little inner group of electrons and protons, but there are more protons than electrons in it; twenty-nine more in fact In an atom there is always an extra proton in the nucleus for each planetary electron That makes the total number of protons and electrons the sa 29 electrons just as if the nucleus was a teacher responsible for 29 children ere out in the play yard There is one very funny thing about it all, however, and that is that we must think of the scholars as if they were all just alike so that the teacher couldn't tell one from the other Electrons are all alike, you remember All the teacher or nucleus cares for is that there shall be just the right nu a boy in froround and the teacher couldn't tell that he was a stranger but she would know that so was the roup She is responsible for just 29 scholars, and the nucleus of the copper atom is responsible for just 29 electrons It doesn't make any difference where these electrons co around the nucleus

If there arepeculiar will happen

We shall see later what ht happen, but first let's think of an enormous lot of atoms such as there would be in a copper wire A small copper ill have in it billions of copper ato their invisible game about their own nucleus There is quite a little distance in any atom between the nucleus and any of the electrons for which it is responsible There is usually a greater distance still between one atoroup and any other

On the whole the electrons hold pretty close to their own circles about their own nuclei There is always soroup With 29 electrons it's no wonder if soame about some other nucleus

Of course, an electron fro and take the place just left vacant, so that nucleus is satisfied

We don't know all we ht about how the electrons wander around from atom to atom inside a copper wire but we do know that there are always a lot of the about in the spaces between the ato one way and so electrons which are affected when a battery is connected to a copper wire Every single electron which is away fro along toward the end of the hich is connected to the positive plate or terative plate That's what the battery does to the the wire