The coordination number of a complex ion refers to the number of ligands molecules or ions that are bonded to the central metal ion. In the case of [Fe H2O 6]2+ complex ion, the central metal ion is Fe2+, and the ligands are six water H2O molecules.Coordination number: The coordination number of the [Fe H2O 6]2+ complex ion is 6, as there are six water molecules acting as ligands and bonding to the central Fe2+ ion.Coordination geometry: The coordination geometry of a complex ion describes the spatial arrangement of the ligands around the central metal ion. For a coordination number of 6, the most common coordination geometry is octahedral. In an octahedral geometry, the ligands are positioned at the vertices of an octahedron, with the central metal ion at the center. The angles between the ligands are 90 degrees.In the case of [Fe H2O 6]2+ complex ion, the six water molecules are arranged in an octahedral geometry around the central Fe2+ ion. This is because the Fe2+ ion has a d4 electron configuration, and the octahedral geometry allows for the most stable arrangement of the ligands and the d-orbitals of the central metal ion. Additionally, the octahedral geometry minimizes electron repulsion between the ligands, leading to a more stable complex ion.In summary, the coordination number of the [Fe H2O 6]2+ complex ion is 6, and its coordination geometry is octahedral. This is due to the stable arrangement of the ligands and the d-orbitals of the central Fe2+ ion, as well as the minimization of electron repulsion between the ligands.