Shapes of complex ions (A-level only)

Transition metal ions commonly form octahedral complexes with small ligands (eg H₂O and NH₃).

Octahedral complexes can display cis–trans isomerism (a special case of E–Z isomerism) with monodentate ligands and optical isomerism with bidentate ligands.

Transition metal ions commonly form tetrahedral complexes with larger ligands (eg Cl⁻).

Square planar complexes are also formed and can display cis–trans isomerism.

Cisplatin is the cis isomer.

Ag⁺ forms the linear complex [Ag(NH₃)₂]⁺ as used in Tollens’ reagent.

MS 4.1 and 4.2

Students understand and draw the shape of complex ions.

MS 4.3

Students understand the origin of cis–trans and optical isomerism.

Students draw cis–trans and optical isomers.

Students describe the types of stereoisomerism shown by molecules/complexes.