Cracks in the Periodic Table (preview)

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The discovery of element 117 filled the last remaining gap in the periodic table as we know it. But even as it is being completed, the table may be losing its power

By Eric Scerri

Image: Holly Lindem

In Brief

• The discovery of element 117 in 2010 completed for the first time the periodic table as we know it?at least until new discoveries will force chemists to extend it by adding a new row.
• Some recent additions, however, may differ in their chemistry from the elements in the same column, breaking the periodic rule that had defined the table for a century and a half.
• The surprising behavior may result from effects described by the special theory of relativity, which make some electron orbits tighter, among other effects.
• Nuclear physicists continue in their quest to synthesize new elements, which will have new types of electron orbitals?and to understand their chemistry from studying a handful of short-lived atoms.

In 2010 researchers in Russia announced they had synthesized the first few nuclei of element 117. This new type of atom does not yet have a name, because the science community traditionally waits for independent confirmation before it christens a new element. But barring any surprises, 117 has now taken its permanent place in the periodic table of elements.

All elements up to 116, plus element 118, had been found previously, and 117 filled the last remaining gap in the bottom row. This achievement marks a unique moment in history. When Dmitri Mendeleev?also Russian?and others created the periodic table in the 1860s, it was the first grand scheme to organize all the elements known to science at the time. Mendeleev left several spaces blank in his table, and he made the bold guess that someday new elements would be discovered that would fill those blanks. Countless revisions of the table followed, but all of them had gaps?until now. With element 117, the periodic table is complete for the first time.

This article was originally published with the title Cracks in the Periodic Table.

Source: http://www.scientificamerican.com/article.cfm?id=cracks-in-the-periodic-table

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