Terry Hall, age 11, of Phoenix, Ariz., for the question:
What is inside an atom?
Atoms were photographed for the first time only three years ago. The ,job was done with a field ion microscope which magnified the tiny particles two million times. Even so, they show up only as blurred pinpoints. There is no detail to show what they are like. Hence, no one has aver seen the inner structure of an atom. What we know about it has bean gathered from careful scientific detective work. Much of it is still guesswork.
It is hard to imagine the size of these tiny particles. If one hundred million atoms. of iron were lined up side by side, they would measure no more than an inch. Suppose you wanted to count them. Allow one second for each number, because some of them are very large. If you do not stop to eat or sleep, you could count the iron atoms in one inch in about three years.
In spite of its small size, the little atom is an orderly unit of still smaller particles. There is still much more to learn about the organization of the particles, but some experts have compared the atom to a miniature Solar System with bitsy planets orbiting a tiny sun. The sun of the atom is its nucleus, which is a wad of tightly bound particles. The nucleus contains one or more protons, depending upon the kind of atom. The nucleus of a hydrogen atom has but one proton. An atom of carbon has six protons in the nucleus and an atom of oxygen has eight. Every proton has a single charge of positive electricity and the protons give the atom its atomic number.
There are also particles called neutrons in the nucleus. These are electrically neutral. There may be one or more than a dozen neutrons depending upon the size of the atom.
Ordinary hydrogen, the smallest of atoms, has no neutrons in its nucleus. There are smaller particles and perhaps clouds of particles in the nucleus and perhaps still more waiting to be discovered. But the two main types of particle in the heart of the atom are the proton and the neutron.
The planets of the atomic Solar System are the electrons particles with a charge of negative electricity. In a normal atom, the number of electrons is equal to the number of protons in the nucleus. This means that the number of positive electrical charges equals the number of negative electrical charges.
Some experts are not certain that the electrons orbit the nucleus. In any case, the orbits are not an a more or less level plane like the planetary orbits of our Solar System. It is suggested they are at various angles, making a sphere around the nucleus.
Our solar planets are millions of miles apart and most of the Solar System is empty space. The atom too is mostly empty space. The single electron which orbits the singly proton of a hydrogen atom has about as much space comparatively as a fly in a movie house.