Robert Harkins, age 11, of College Park, Georgia, for his question:

Why is radium so important?

Any list that rated the atomic elements in the order of their importance would place radium near the top. Actually there are two very different reasons for its outstanding importance. One is the unique role it played in the history of science. The other is its dramatic usefulness to mankind.

The earth's most plentiful element is oxygen. It is vital to plants and animals and the world of living things could not survive without it. Certainly in terms of usefulness oxygen would rate as the most important of the earth's 92 chemical elements. It makes up almost half of the earth's crust. The element radium makes up less than one billionth part of the earth's crust. Small traces of its atoms are concealed in mixtures with other minerals and radium is hard, very hard to come by. The earth also has scanty supplies of many other rare elements. Most of us hardly ever hear of them and few of us know their names. But all of us have heard about radium and know that it is important.

Its sudden rise to chemical stardom began in 1898 when Marie and Pierre Curie first separated this strange unknown element from tons of pitchblende ore. It was discovered to be an extremely radioactive element. And this opened the door to an entirely new dimension of the chemical sciences.

Investigation proved that in any given quantity of radium a fixed number of nuclei could be trusted to break apart by themselves at a precise ratio every moment. The basic nature of an atom depends upon the structure of its nucleus. When its nucleus loses a proton particle it becomes an atom of another element. The study of radium did much to illuminate this dramatic new concept of radioactivity. It helped unlock the atomic nucleus and reveal its unknown particles and energies. Our uses of nuclear energy and the creation of new man made elements spring in part from the historically important dis¬covery of radium.

As the nuclei of radioactive radium break apart, they emit streaming rays of high speed alpha and beta particles and penetrating gamma rays of energy somewhat similar to penetrating X rays. Scientists soon discovered that these dangerous radium emissions can be used to do life saving work. Compounds of radium are expertly guided to destroy cancerous cells in living tissue. Certain researchers use traces of radium to probe the biological processes of life itself. Aside from its historic importance, radium plays a top level role of importance in biology and the life saving science of medicine.

Ninety tons of uranium ore yield less than one ounce of radium and the complex job of extracting it is expensive. And since its radioactive atoms constantly decay, the supply on hand is depleting. After 1,660 years, half of the original ounce will have disintegrated into radon gas and nuclear energy. A quarter ounce, half the remaining supply, will decay in the next 1,660 years. This 1,660 year period is the half life of radium    the strict ratio at which its radioactive decay progresses.