Philip Ball in New Scientist:
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.