Final answer:
For a metal ion with a magnetic moment of 4.90 BM, the formula used to calculate unpaired electrons suggests approximately three unpaired electrons are present. This conclusion is based on the relationship between the number of unpaired electrons and the size of the magnetic moment.
Step-by-step explanation:
The calculated magnetic moment of 4.90 Bohr Magnetons (BM) for a metal ion indicates the presence of a certain number of unpaired electrons. To determine the number of unpaired electrons from the magnetic moment, you can use the formula √(n(n+2)), where n is the number of unpaired electrons.
In this case, with a magnetic moment of 4.90 BM, we have approximately 4.90 = √(n(n+2)). Solving for n gives us a value of nearly 3, which means that the metal ion should have about three unpaired electrons, leading to its paramagnetic behavior.
Examples of calculated magnetic moments can be seen in high-spin d6 [Fe(H2O)]2+, which has four unpaired electrons and in low-spin d0 [Fe(CN)6], which shows that iron is diamagnetic with no unpaired electrons. The presence of unpaired electrons is directly related to the magnitude of the magnetic moment, with a larger number of unpaired electrons resulting in a larger magnetic moment.