The electronic configuration of transition metals like iron, cobalt, and nickel plays a crucial role in determining their reactivity towards ligands in coordination compounds. To understand this, let's first look at the electronic configurations of these elements:Iron Fe : [Ar] 3d^6 4s^2Cobalt Co : [Ar] 3d^7 4s^2Nickel Ni : [Ar] 3d^8 4s^2In transition metals, the 3d and 4s orbitals are relatively close in energy, and electrons can be easily removed from both orbitals. When these metals form coordination compounds, they lose electrons from the 4s orbital first, followed by the 3d orbital, to form positively charged metal ions. These metal ions can then accept electron pairs from ligands to form coordination compounds.The reactivity of these transition metals towards ligands is determined by several factors:1. Number of unpaired electrons: The number of unpaired electrons in the d-orbitals of the transition metal ions determines their ability to form coordination compounds. More unpaired electrons mean more available orbitals for ligands to bind, resulting in higher reactivity. For example, Fe II has 4 unpaired electrons, Co II has 3, and Ni II has 2, making Fe II more reactive towards ligands than Co II and Ni II .2. Crystal field stabilization energy CFSE : The energy difference between the metal-ligand bonding and non-bonding orbitals, known as crystal field stabilization energy, also affects the reactivity of transition metals towards ligands. A higher CFSE means stronger metal-ligand bonds and greater stability of the coordination compound. Transition metals with higher CFSE are more likely to form stable coordination compounds with ligands.3. Oxidation state: The oxidation state of the transition metal ion affects its reactivity towards ligands. Higher oxidation states usually result in a stronger metal-ligand bond and a more stable coordination compound. However, very high oxidation states can also lead to increased instability due to the high positive charge on the metal ion.4. Nature of the ligand: The type of ligand also influences the reactivity of transition metals in coordination compounds. Some ligands, known as strong-field ligands, cause a larger splitting of the d-orbitals, resulting in a higher CFSE and more stable coordination compounds. In contrast, weak-field ligands cause smaller splitting and lower CFSE, leading to less stable compounds.In summary, the electronic configuration of transition metals like iron, cobalt, and nickel determines their reactivity towards ligands in coordination compounds through factors such as the number of unpaired electrons, crystal field stabilization energy, oxidation state, and the nature of the ligand. These factors influence the stability and strength of the metal-ligand bonds, ultimately affecting the reactivity of the transition metals in forming coordination compounds.