The synthetic elements through at. no. 100 (fermium) are created by bombarding a heavy element, such as uranium or plutonium, with neutrons or alpha particles. The synthesis of the transfermium elements (elements with at. no. 101 or greater) is accomplished by the fusion of the nuclei of two lighter elements. Elements 101 through 106 were first produced by fusing the nuclei of slightly lighter elements, such as californium, with those of light elements, such as carbon. Elements 107 through 112 were first produced by fusing the nuclei of medium-weight elements, such as bismuth or lead, with those of other medium-weight elements, such as iron, nickel, or zinc. Most of the elements with at. no. 113 through at. no. 118 were discovered by bombarding plutonium, americium, or a heavier transuranium element in the actinide series with calcium; the Japanese scientists who synthesized element 113, however, fused bismuth with zinc.
The transfermium elements are produced in very small quantities (one atom at a time), and identification is therefore very difficult because of half-lives ranging from minutes to milliseconds and the need to identify the products by methods other than known chemical separations. This has led to controversy over reported discoveries and over the naming of the elements. It has been predicted that one isotope of element 114—containing 114 protons and 184 neutrons—would be very stable because its nucleus would have a full complement of protons and neutrons. Termed an
island of stability, its half-life might be measured in years. However, none of the isotopes of element 114 synthesized as yet have as many as 184 neutrons, and their half-lives are still in the millisecond range (see flerovium).
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