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Q.
Which of the following transition metal series favors the formation of low spin complexes?
Coordination Compounds
Solution:
When the complexes of transition metal ions are formed, the degeneracy of ' $d$ ' orbitals is removed and the two set of ' $d$ ' orbitals $d_{Z^{2}}, d_{x^{2}-y^{2}}$ and $d_{x y}, d_{x z}, d_{z y}$ split in energy.
This is known as crystal field splitting. Now, this crystal field splitting in case of metals of $4 d$ and $5 d$ transition series is much larger. Therefore, the electron of the metal ion are paired up first in low energy set of orbitals before going to the higher energy set within the same ' $d$ ' subshell, causing maximum pairing and low spin complexes are formed.