Final answer:
The ratio of EDTA to a metal ion is usually 1:1, as EDTA is a hexadentate ligand which forms stable chelate complexes with metal ions.
Step-by-step explanation:
The ratio of EDTA to a metal ion is typically 1:1. This is because EDTA is a hexadentate ligand, meaning it has six points of attachment, allowing it to form stable complexes with metal ions. The ligand binds to a metal ion by wrapping around it and utilizing all six coordinate bonds, creating a 1:1 stoichiometric chelate complex.
The overall charge of the complex is determined by combining the charges of the metal ion and the EDTA. For instance, with a copper(II) ion (which has a 2+ charge) and the EDTA ion (which has a 4- charge), the resulting EDTA-metal complex would have a net charge of (2+) + (4-) = 2-. EDTA's ability to form such complexes is also why it is utilized as a chelating agent in various applications, including medical treatments for heavy metal poisoning.