Becky Wieser, age 10, of Muncie, Indiana., for her question:

How can a tiny atom split?

It takes about 100 million atoms of iron to measure one inch. The strongest microscopes can photograph the dim shadows of larger atoms, but no human eye has ever seen one. A thoughtful person naturally wonders how such tiny things can be split apart. This is possible because every tiny atom is built from even tinier particles. Particles around the outside often get lost without splitting the atom. But something very dramatic happens when a particle is lost from the tight central core. Then the atom splits apart and becomes a different atom.

Atoms can be split by mighty, man made atom smashers and some atoms split apart all by themselves. The up to date term for atom splitting is nuclear fission. The word fission means to split or break apart. The word nuclear refers to the nucleus, that tight fisted core in the center of an atom. Particles called electrons swarm around the nucleus, somewhat like planets orbiting around the sun. Atoms are always losing or swapping their outer electrons. But nuclear fission happens only when particles are lost from the nucleus.

A mighty atom smasher can do this by whipping up particles to enormous speeds and aiming them like minuscule bullets. They are aimed at a target, which may be a piece of metal. The target, of course, is made of tiny atoms and each atom has a tight¬fisted nucleus amid a swarm of electrons. Many of the atom smashing bullets zoom harmlessly through the electrons and the spaces between the atoms. But a lucky one strikes a nucleus and. upsets its delicate balance. When the upset splits the nucleus, it loses one or more of its particles and also shoots off some of its mighty atomic energy.

This nuclear fission is upsetting because the nucleus of each atom must be just so. Its mighty energy binds together a certain number of protons and other assorted particles in a tight wad. Our everyday world is built from just 92 different atoms called the chemical elements. Each has its own atomic number that tells the number of protons in its nucleus. The numbers range from one to 92, plus several larger man made atoms. For example, iron is atomic number 26. If the nucleus of an iron atom split and lost a proton, only 25 would be left. It would then be an atom of manganese, which has atomic number 25.

The large uranium atom has atomic number 92. If it loses one proton, it becomes a rare element called protactinium    and shoots off spurts of its nuclear energy. Atom smashers can do this, though the cost of protactinium is about half a million dollars an ounce. But it so happens that nature's uranium atoms split apart all by themselves. Its heavy atoms break down stage by stage into smaller and smaller atoms    and each stage gives off nuclear energy. One of these complicated stages forms protactinium number 91    but its atoms soon change into other atoms.

In the age of science, we released the energy of nuclear fission to make atomic bombs. Later we tamed the energy from these splitting atoms to run useful electric power plants. We call it atomic energy, though actually it comes from only the nucleus part of the atom. It is released when zillions of tiny nuclei split apart and shoot off some of the mighty energy that binds the tight wads of particles together.