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| A new kind of alchemy |
| 2005-04-15 |
| LET'S hear it for Dmitri Mendeleev. His periodic table has done a remarkable job of making sense of the elements, arranging them neatly into families whose members share similar properties. For more than a century it has been chemists' guiding light. But Mendeleev's classic layout is starting to prove inadequate at describing the unexpected ways in which chemical elements behave when divvied up into small chunks. And now some chemists think it may be time to build a whole new table, this time from something much stranger than atoms: superatoms. According to Mendeleev's roll call, an element's chemistry can be deduced from where it sits in the periodic table. Reactive metals like sodium and calcium occupy the two columns on the left. The inert "noble" gases make up the column on the far right, flanked by typical non-metals such as chlorine and sulphur. Now this neat picture is being disrupted by superatoms - clusters of atoms of a particular chemical element that can take on the properties of entirely different elements. The chemical behaviour can be altered, sometimes drastically, by the addition of just one extra atom. "We can take one element and have it mimic several different elements in the periodic table," says Welford Castleman, an inorganic chemist at Pennsylvania State University who has studied the chemistry of aluminium superatoms. It is a finding that is challenging our entire understanding of chemical reactivity. Adding superatoms to the periodic table would transform it from a flatland to a three-dimensional landscape in which each element is drawn out into a series of super-elements. Superatoms could have practical uses too: they could be combined into super-molecules to make new materials. And their unusual chemistry could be harnessed to make efficient fuels. |
| Posted by:Sobiesky |