The coordination geometry of the complex [UO2 H2O 5]2+ is pentagonal bipyramidal. In this complex, the uranium atom U is at the center, and it is bonded to two oxygen atoms O in the axial positions, forming a linear U-O-U unit. The five water molecules H2O are coordinated to the uranium atom in the equatorial plane, forming a pentagonal arrangement.On the other hand, the coordination geometry of the isoelectronic complex [Th H2O 6]4+ is octahedral. In this complex, the thorium atom Th is at the center, and it is surrounded by six water molecules H2O in an octahedral arrangement.The main difference between the coordination geometries of these two complexes is the number of ligands and the arrangement around the central metal atom. In [UO2 H2O 5]2+, there are seven ligands two oxide ions and five water molecules in a pentagonal bipyramidal arrangement, while in [Th H2O 6]4+, there are six ligands six water molecules in an octahedral arrangement.