What is the geometry of the complex ion [Cr(H2O)4Br2]+?

• A. Square planar
• B. Tetrahedral
• C. Trigonal bipyramidal
• D. Octahedral

Answer: (D)

Verified step by step guidance

1. Identify the central metal ion and its coordination number. In the complex ion [Cr(H2O)4Br2]+, chromium (Cr) is the central metal ion, and it is bonded to 6 ligands (4 water molecules and 2 bromide ions), so the coordination number is 6.
2. Recall that the coordination number often determines the geometry of the complex. For coordination number 6, the most common geometry is octahedral.
3. Consider the nature of the ligands: both H2O and Br- are monodentate ligands, meaning each occupies one coordination site, so no special geometrical distortions are expected from ligand denticity.
4. Visualize or draw the complex with the six ligands arranged around the chromium ion. The ligands will be positioned at the vertices of an octahedron, with 90° angles between adjacent ligands.
5. Conclude that the geometry of [Cr(H2O)4Br2]+ is octahedral based on the coordination number and typical ligand arrangement for six-coordinate complexes.