Periodic Table

While the general form of the periodic table has withstood the test of time and should change very little in the future, alterations of the periodic table have been and continue to be made. One area that could see minor changes is the atomic mass. In the future more accurate methods of measuring the mass of atoms may be invented. The magnitude of these changes, however, would be exceedingly small.

The largest area of change in the periodic table will come from the manmade creation of new chemical elements. Every element past uranium in the periodic table has been made by scientists in high energy particle accelerators. The first transuranium element made was element 93, discovered by E. M. Macmillan and P. H. Abelam at the University of California at Berkeley in 1940. The two discoverers of this element named it neptunium (Np).

The discovery of elements 95, americium (Am), and 96, curium (Cm), caused a dilemma. It was thought that these new elements should be placed after element 89, actinium (Ac) in the d-block transition metal family. Glenn T. Seaborg, Nobel Prize winner in 1951 for the discovery of plutonium (Pu) as well as nine other transuranium elements, felt that they should be placed under the lanthanides in a new group as part of the inner transition metal family. Further experimentation showed that they did belong in the inner transition metal family. The discovery of elements 104-111, which belong in the transition metals family, proved that the proposed groupings were correct.

Unlike most of the naturally occurring elements, which can be handled and studied, the transuranium elements are all radioactive and break down incredibly fast. The synthesis and detection of transuranium elements takes great technical expertise. In addition, the experimental machinery needed to do this work is extremely expensive as well as complicated, therefore only a few research centers in the world are involved in this area of study.

The transuranium elements are synthesized by colliding accelerated charged particles with heavy atoms (i.e., curium and lead). In certain collisions the nuclei of the accelerated charged particles and the stationary heavy atoms will fuse to produce a new transuranium element. The lifetimes of these new elements are so short they often break down into other elements within fractions of a second and are detected only by their breakdown products, referred to as daughter elements.

Recently, several new manmade "superheavy" elements have been discovered. These include elements 110 and 111, both of which were made in late 1994 by an international team of scientists. These scientists performed this research at GSI, a research center for heavy ion research in Darmstadt, Germany. Element 110 was made by colliding nickel atoms with an isotope of lead. Researchers in Russia have plans to make a different isotope of element 110 by colliding sulfur atoms with plutonium atoms. Elements 116 and 118 were recently discovered at a Berkeley laboratory. Other superheavy elements which have been predicted to exist have yet to be made in the laboratory, although research continues into the creation of these elements.

Based on theoretical calculations some researchers believe that not all transuranium elements will be so unstable. Already, different isotopes of element 106, seaborgium (Sg) have been made that are stable for up 33 times longer than the original isotope discovered in 1974 (even at 33 times longer lifetime it only is stable for a maximum of thirty seconds). It is theorized that some isotopes of the yet to be made transuranium elements should be stable for very long periods of time, allowing them to be studied chemically. Many exciting discoveries remain to be uncovered concerning the creation of new elements, and with the periodic table as a guide, their place is already awaiting them.