AIIMS 2018 Chemistry Ligands and Coordination Number Assertion Reason Question

In Zieser's salt, the coordination number of platinum is indeed 4 because the ethene ligand acts as a bidentate ligand, coordinating through two points of attachment, which allows for a square planar geometry rather than a five-coordinate structure. Therefore, the assertion that the coordination number is 4 is true, while the reason provided—that ethene is a monodentate ligand—is false. This makes option B correct, as both the assertion is true and the reason is false. Other options are incorrect because they do not accurately reflect the nature of ethene as a bidentate ligand, which is essential for understanding coordination chemistry in transition metal complexes.