The oxidation state of Mo in its oxo-complex species \(\left[\mathrm{Mo}_{2} \mathrm{O}_{4}\left(\mathrm{C}_{2} \mathrm{H}_{4}\right)_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\right]^{2-}\) is: (a) \(+2\) (b) \(+3\) (c) \(+4\) (d) \(+5\)

Coordination chemistry involves the study of compounds formed between metal ions and ligands, which are molecules or ions capable of donating a pair of electrons to the metal, creating coordination complexes. A coordination complex consists of a central atom, typically a metal cation, surrounded by a number of bound molecules or anions, known as ligands.

Oxidation states in coordination complexes are determined by the charge on the metal plus the charges contributed by the ligands. In the given exercise, we looked at the oxo-complex species \[\left[\mathrm{Mo}_{2}\mathrm{O}_{4}\left(\mathrm{C}_{2}\mathrm{H}_{4}\right)_{2}\left(\mathrm{H}_{2}\mathrm{O}\right)_{2}\right]^{2-}\], where Mo stands for molybdenum, a metal ion that forms the core of the complex. The oxygen atoms and water molecules are neutral ligands, while oxygen in the \(\mathrm{O}_{4}\) group has a -2 oxidation state each, which contributes to the total oxidation calculation for molybdenum.

Redox reactions, short for reduction-oxidation reactions, are chemical processes where the oxidation state of atoms is changed. These reactions are characterized by the transfer of electrons between chemical species. Oxidation refers to the loss of electrons, while reduction refers to the gain of electrons.

In coordination complexes like the one in our exercise, a redox reaction can modify the oxidation state of the metal center as it interacts with other species. It's important to understand the concept of 'oxidation state' when studying redox reactions as it helps predict the behavior of chemical species during these reactions. Oxidation states provide a way to keep track of electrons as they are transferred in redox processes, which is a foundational concept when working through problems in coordination chemistry.

The National Eligibility cum Entrance Test (NEET) is a significant pre-medical examination in India, for which chemistry is a vital subject, including physical chemistry topics like coordination chemistry and redox reactions. As part of NEET chemistry preparation, understanding how to calculate oxidation states is essential.

For exercises involving the calculation of oxidation states in complex species, as shown in the given problem, mastery over the assignment of proper oxidation numbers to different elements and understanding their significance in predicting the behavior of compounds is crucial. Preparing for these types of questions involves not only memorizing the rules for determining oxidation states but also practicing a multitude of problems to gain confidence and accuracy.