Greek claws

In Monday’s posting I mentioned that lead could be removed from the body by using a chelating agent. But what is a chelating agent? This is not part of the IB course but is an interesting phenomena.

Building on existing knowledge from topic 13.2 (Periodicity –> ‘d’ block / transition metal elements) you will know about ligands and complex ions.

The ligands we study (eg, H₂O, NH₃, Cl^– ) are referred to as unidentate ligands – they only form one dative covalent bond.

The are also, however, bidentate and multidentate ligands (species that from two dative bonds, four dative bonds or even six dative bonds):

The bidentate and multidentate ligands are also referred to as chelates and the process of forming the dative bonds is called chelation. This is where we meet our Greek claws – the words chelate and chelation are derived from the Greek work for claw and we can imagine these ligands gripping onto or surrounding the central metal ion.

Chelates form very very very stable complexes and the reason why is also quite interesting*. However, more about this tomorrow …..

* If you know why they are so stable, post your reply below – you have 24 hrs!