How do chelating agents like EDTA treat heavy-metal (lead) poisoning?
EDTA is a polydentate ligand that wraps around a metal ion at six points, forming a very stable, water-soluble chelate ring.
EDTA is a polydentate ligand that wraps around a metal ion at six points, forming a very stable, water-soluble chelate ring. Given to a poisoned patient, it grabs toxic lead ions from the tissues into this tight complex, which the kidneys then excrete. The multi-point 'claw' grip (the chelate effect) makes the complex far more stable than water or simple ligands around the metal.
Key point
A chelating (polydentate) ligand forms an extra-stable ring complex that locks up and removes the metal ion.
Common mistake
thinking a single-point ligand would hold the metal just as tightly.
Memory tip
'chelate' = claw: many-point grip → very stable complex → metal removed.
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