The magnetic moment of a complex ion can be calculated using the formula: = n n+2 BM Bohr Magneton where n is the number of unpaired electrons.First, we need to determine the oxidation state of Fe in the [Fe H2O 6]2+ complex ion. Since the overall charge of the complex ion is +2 and water H2O is a neutral ligand, the oxidation state of Fe is +2.Fe in the +2 oxidation state has an electron configuration of [Ar] 3d6, which means it has 6 electrons in its 3d orbitals.Now, we need to determine the number of unpaired electrons. In the case of Fe2+, the 3d orbitals are filled as follows: using Hund's rule . There are 4 unpaired electrons.Now, we can calculate the magnetic moment: = n n+2 BM = 4 4+2 BM = 4 6 BM = 24 BM 4.90 BMSo, the magnetic moment of the [Fe H2O 6]2+ complex ion is approximately 4.90 Bohr Magnetons.