How to determine if ligands are polydentates?

[Eugenia Kwon 3O]

This question is based on the homework question 33 in chapter 17; I understand that ligands have an atom with an electron pair to donate to form a coordinate bond; but how do you determine e.g. whether H2O is a monodentate and CO3(2-) is a mono/bidentate?

[Kristina Mercolino 3C]

I think the number of lone pairs on separate atoms in the ligand for the transition metal to bind to determines if the ligand is monodentate or polydentate. Since H2O has both lone pairs on one oxygen atom, it is monodentate.

[Shushanna S 3F]

What kind of dentate a ligand is depends not only on the number of atoms with lone pairs, but also on the geometry. For example, the best structure for a bidentate molecule is the half ring. With the atoms with lone pairs separated by two spacers.