Formation of Low Spin Complexes by Transition Metals

Low spin complexes are those complexes in which the electrons tend to occupy the lower energy orbitals before the higher energy orbitals. The formation of low spin complexes is dependent on the electronic configuration of the metal ion. Generally, transition metals form low spin complexes due to the following reasons:

1. High Nuclear Charge: Transition metals have a high nuclear charge, which results in strong attraction between the nucleus and the electrons. This results in a small atomic radius and a high effective nuclear charge, which leads to a low energy difference between the d-orbitals.

2. Ligand Field: Ligands are molecules or ions that surround the metal ion and form a complex. The ligands create a ligand field, which affects the energy levels of the d-orbitals. The ligand field can be of two types, high spin or low spin. In low spin complexes, the ligand field is weak, and the energy difference between the d-orbitals is small.

3. Electronic Configuration: The electronic configuration of the metal ion determines whether it will form a low spin or high spin complex. For example, the d5 configuration of Mn2+ will form a low spin complex, while the d4 configuration of Cr2+ will form a high spin complex.

Elements that Form Low Spin Complexes

The elements that form low spin complexes are those that have a high nuclear charge and a small atomic radius. These elements belong to the 3d, 4d, and 5d series. Therefore, option D, which states that low spin complexes are generally formed by the elements of both the 3d and 4d series, is the correct answer.

Conclusion

In conclusion, low spin complexes are formed by transition metals due to their high nuclear charge, ligand field, and electronic configuration. The elements that form low spin complexes belong to the 3d, 4d, and 5d series. Therefore, option D is the correct answer.