PrayogX › Chemistry › Coordination Compounds

Triangular faces of cis and mer octahedral complexes carrying one N and two Cl

Type the composition of each coordination sphere into the panel, press Run experiment, and watch a model octahedron get built, its six numbered sites loaded with N and Cl donors, and each of its eight triangles turned towards you in turn while an inspector tallies the ones matching the pattern - the answer is the tally at the end, and it blinks when it lands.

Sub-topics covered

• Coordination sphere versus counter-ion
• Geometry of the octahedron: vertices, edges and faces
• cis and trans isomers of an MA4B2 complex
• fac and mer isomers of an MA3B3 complex
• Counting faces by their corner composition
• Edges shared between faces

What it teaches

• Only what is inside the square brackets is bonded to the metal - the chloride written outside is the counter-ion and never reaches a vertex
• The six sites are numbered the usual way - 1, 2, 3, 4 round the square plane and 5, 6 axial - so the opposite (trans) pairs are 1-3, 2-4 and 5-6 and every other pair is cis
• An octahedron has 6 vertices, 12 edges and 8 triangular faces, and every face takes exactly one vertex from each opposite pair
• cis means 90 degrees apart, so two cis donors share an edge; trans means opposite, so no face contains both
• fac means three mutually cis donors, which form one whole face; mer means one pair is trans and the third is cis to both
• Every edge of an octahedron lies in exactly two faces, so a Cl-Cl edge contributes two faces carrying two chlorides
• A count like this depends only on the isomer label, not on which particular vertices are drawn

Simulation ID

• ADV-2026-P2-CHE-Q13 · revision 2

See this simulation in the library →  ·  open the simulation file on its own