The total number of stereoisomers for the complex $$[Cr(ox)_2ClBr]^{3-}$$ (where ox = oxalate) is

The complex [Cr(ox)₂ClBr]³⁻ has chromium with two bidentate oxalate ligands and two monodentate ligands (Cl and Br).

This is an octahedral complex of the type [M(AA)₂ab] where AA is a bidentate ligand and a, b are different monodentate ligands.

For [M(AA)₂ab] type complexes, there are 3 possible stereoisomers:

• cis isomer (Cl and Br on same side): This has no plane of symmetry, so it exists as a pair of optical isomers (Δ and Λ). That gives 2 isomers.
• trans isomer (Cl and Br on opposite sides): This has a plane of symmetry, so only 1 isomer.

Total stereoisomers = 2 (optical) + 1 (trans) = 3.

This matches option 1: 3.