UT Chemist Determines Element’s Fundamental Properties (285)

 KNOXVILLE, Tenn. — A University of Tennessee scientist’s experiment with a rare element has helped confirm that element’s place on the periodic chart.

 Dr. Joe Peterson, a UT-Knoxville and Oak Ridge National Laboratory chemist, said the periodic chart lists elements in order of atomic number and shows periodic variations in their properties. This enables scientists to predict chemical and physical behaviors of elements, he said.

 However, in the heavy elements, these behaviors can change due to what are known as relativistic effects, which occur as electrons approach the speed of light, Peterson said.

 Scientific estimates based on the periodic chart may not be accurate for the heavy elements, known as actinides, he said.

 “The architecture of the periodic chart will eventually break down due to relativistic effects,” Peterson said. “The problem is, we do not know where that change will occur.”

 Peterson has helped solve the problem for at least one actinide element: einsteinium-254, a rare, heavy element produced only in special reactors at ORNL.

 Using sophisticated laser and mass spectroscopy equipment available only at the University of Mainz, Germany, Peterson and some German colleagues found that it takes 6.3676 electron volts, very small units of energy, to separate an electron from an atom of einsteinium.

 This measurement, known as the element’s first ionization potential, tells scientists about the electronic structure and relativistic effects of an element, Peterson said.

 “Prior to the Mainz project, no such measurement on einsteinium had been made,” Peterson said. “This research helps us understand these trends and changes in the actinide elements.

 “It confirms that current information about the heavy elements is reliable and accurate.”

 Peterson will present a paper on the project in September at the Actinides 1997 Conference in Baden-Baden, Germany.

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 Contact: Dr. Joe Peterson (423-974-3434, 574-5016)