Select the incorrect statement:

Hydrazine can act as a bidentate ligand.

The correct option is (1) Hydrazine can act as a bidentate ligand.

The correct statement is:

Hydrazine (H₂N-NH₂) as a monodentate ligand: A ligand is a molecule or ion that can donate a pair of electrons to a central metal atom or ion to form a coordination complex. Hydrazine, with two amine groups (H₂N-NH₂), can indeed donate a lone pair of electrons from one nitrogen atom to form a coordinate bond with a metal center, making it a monodentate ligand.

Bidentate ligands and chelating ligands: A bidentate ligand is a ligand that can coordinate to a metal center by donating two lone pairs of electrons from two separate atoms in the ligand. Bidentate ligands can create a ring-like structure when coordinated to a metal center, and this phenomenon is referred to as chelation. Chelating ligands are a subset of bidentate ligands that can form such ring structures (chelates) when attached to a metal ion.

Oxalate as a bidentate ligand: Oxalate is indeed a bidentate ligand. It contains two carboxylate groups (-COO^-) capable of donating lone pairs of electrons to form two coordinate bonds with a metal center. When coordinated to a metal ion, oxalate forms a chelate ring.