Technetium (Chemical Elements)
Technetium is the only element below uranium that does not exist on Earth. It is a synthetic (man-made) element produced in a particle accelerator. For many years, chemists knew that an element with atomic number 43 must exist, based on an empty spot in the periodic table. The periodic table is a chart that shows how chemical elements are related to each other. By 1925, only five empty boxes remained. Five elements were still to be discovered.
A number of scientists tried to find those elements. In many cases, the results they announced were wrong. Such was the case with element 43. When the element's "discovery" was announced in 1925, chemists were excited, but no one else was able to repeat the discovery. An error had been made. In fact, it was not until more than ten years later that the element was finally produced. Then, it was created in a particle accelerator and not found on Earth.
(The entire section is 1147 words.)
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