Thursday, April 27, 2006

A cluster of atoms

Author: Khalil A. Cassimally

Imagine a new variety of compounds; compounds that have properties never seen before or simply compounds that have properties more pronounced than those which we already know of at present. It would be really cool. No, in fact it is really cool! Indeed, an entirely new class of compound is on the verge of getting everybody’s attention.

Only some times back, it has been shown that a new division of compounds could exist. A new study now confirms the idea that a cluster of atom of an element, behaves differently from a single atom of the element. It is as if, a new element is being created.

For example, a cluster of 13 aluminium atoms behaves like a halogen (chlorine, bromine, iodine, etc). In addition, the aluminium cluster can react with halogens to form halogen compounds with novel properties!

However a cluster of one more aluminium atom, that is to say, 14 aluminium atoms, will act not like a halogen but rather like an alkaline earth (calcium, barium, etc) atom. And the ions that are hence formed are in fact totally new types of salts! For instance, when the 14 aluminium atom cluster reacts with 3 iodine atoms, an ion with an absolute charge of –3 is formed. Surprisingly this resulting ion is very stable.

The atom cluster thing has also been a source of debate in the scientific community. According to Shiv Khanna, co-leader of the study, the periodic table must be altered to accommodate the clusters or ‘superatoms,’ as he calls them.

How? Simple. Just add a 3rd dimension to the periodic table. The 13 aluminium atom cluster will then be in the same row and column as iodine since it acts more or less like the latter. Only difference is that it will be in a new plane. Same thing for the 14 aluminium atom cluster in the alkaline earth group and for the other ‘superatoms.’

As if the periodic table wasn’t complicated enough! But I guess that it will be even more so if the additions are made. So don’t you dare think that your generation’s college chemistry was hard!

About the author: Khalil A. Cassimally is currently Senior Columnist at and Columnist for h2g2 The Post where he writes 'Not Scientific Science' column.


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