Prior to the atomic age, scientists believed uranium was the heaviest element with an atomic number of 92. However, this was shown to be wrong because a number of transuranium elements have been produced. Today, researchers have created elements at each position on the periodic table through element 112. No one knows exactly how many more elements exist, but current theory holds that there is a maximum of 200 possible.

Heavy elements are produced by a variety of techniques. One method that is often used is to bombard a lower transuranium element, such as plutonium, americium, or curium, with alpha particles or ions of light elements. The following is a typical example:

Element 104 is of interest to chemists because it is the first transactinideelement, that is, the first element to begin a new rare-earth-type row in the periodic table. It occupies the space below hafnium in the table...