[zilalti]

From what I understand there is the trend of metal ligand bond strengths increasing down the group for transition metals. All the papers I have read give the explanation that it is due to relativistic stabilization? What exactly is this? Is anything to do with electrons going faster and therefore getting heavier i.e. einsteins relativity?  Or is there something more?

[kimyacı]

 To me it is related to increasing covalent character of metal down group