Steve Gilbowski, age 16, of Camden, N.J., for his question:

WHAT EXACTLY IS EINSTEINIUM?

Einsteinium is one of the man made radioactive elements. Its atomic number is 99 and the most stable isotope of einsteinium has a mass number of 254.

The element was named in honor of the famous scientist Albert Einstein. It came about as a result of the effort of scientists at the University of California, the Argonne National Laboratory and the Los Alamos Scientific Laboratory.

Einsteinium was first discovered in 1952 in the debris from a hydrogen bomb explosion. Scientists collected this debris on filter papers carried by radio controlled airplanes and from fallout on a nearby coral atoll. This new element formed when neutrons from the explosion hit atoms of uranium 238 and were captured by its nucleus. Fermium, element 100, was formed at the same time.

Scientists first made einsteinium in a laboratory in 1954, but only minute quantities of the element have been produced.