The coordination number of a compound is the number of ligands atoms, ions, or molecules that are directly bonded to the central metal atom or ion. In the given compound, [Fe H2O 6]3+, the central metal atom is Fe iron , and it is surrounded by six H2O water molecules acting as ligands.Therefore, the coordination number of the compound [Fe H2O 6]3+ is 6.The geometry of a complex with a coordination number of 6 is typically octahedral. In an octahedral geometry, the central metal atom/ion is surrounded by six ligands at equal distances, with 90-degree angles between them. So, the geometry of the complex [Fe H2O 6]3+ is octahedral.