Fran Kane, age 13, of Los Angeles, Calif., for the question:
What is a neutron?
The words neutron, neutral and neither are related. The neutron is a neutral atomic particle, having neither a positive charge of electricity nor a negative charge. An atomic particle, of course, is one of the building blocks of the tiny atom. Everything around use is made from atoms which measure, on the average, about 100 million to an inch. A pencil is an assortment of atoms, numbering perhaps 1,000 Followed by 21 zeros. Moat of those atoms contain at least one neutron.
The pencil, teeming with atoms, and anything else we are likely to touch, will b e electrically neutral, This makes us wonder why neutrality is such an important feature of the neutron. We find the reason by comparing it with the two other important atomic particles. One is the "electron, a single charge of negative electricity. The other is the proton, a single charge of positive electricity. There are other atomic particles, but these three are the important ones.
A normal atom has an equal number of protons and electrons. The positive and negative electricity, then, cancel each other out and the atom is electrically neutral. The pencil is made from normal, electrically neutral atoms. The number of protons 1n an atom is fixed. Hydrogen has on®, oxygen has six and carbon has eight. The number of neutrons may vary. The smaller atoms have one or two, the largest have perhaps a hundred.
The make‑up of the atom has been compared to a miniature solar system, The central sun is the atomic nucleus which contains more than 99 per cent of the atom s weight. It is a tightly bound bundle of proton and neutron particles. The planets of this tiny solar system are the orbiting electrons,
Each proton weighs as much as 1,$36 electrons and a neutron weighs a little more than a proton. If the electrons and their orbits could be sheared away and the nuclei packed together, we would have a very dense and heavy material. A marble made of this stuff would weigh perhaps a billion tons.
The smallest atom is hydrogen, with one proton, one electron and no neutron. But this atom of common hydrogen has a number of brothers called isotopes. One hydrogen isotope has one neutron in the nucleus and one has two. How can we tell them apart? A neutron, remember, weighs a. little more than a proton. An atom of hydrogen with a neutron weighs about twice as much as an ordinary hydrogen atom. In fact, it is sometimes called heavy hydrogen.
Isotopes of most elements have been found and many of them have been put to work. Many of the isotopes are radioactive. They are often used as tracers to follow the biological processes going on in living plants and animals, Some of the isotopes have done valuable work in the field of medicine. Others are useful as atomic fuels: .