MHTCET 25 Apr 2025 Shift 2 Paper

Concept:The effective atomic number (EAN) of a metal in a complex is calculated using the formula $\mathrm{EAN} = Z - O + N$.Explanation:In the formula, $Z$ is the atomic number of the metal, $O$ is the oxidation state of the metal, and $N$ is the total number of electrons donated by all ligands.For zinc, the atomic number is $Z = 30$.In the complex $\left[\mathrm{Zn}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+}$, the ligand $\mathrm{NH}_3$ is neutral, so the overall charge of $+2$ gives the oxidation state of $\mathrm{Zn}$ as $O = +2$.Each $\mathrm{NH}_3$ ligand donates 2 electrons, and there are 4 such ligands, so $N = 4 \times 2 = 8$.Substituting these values: $\mathrm{EAN} = 30 - 2 + 8 = 36$.Answer:The EAN of $\mathrm{Zn}$ in $\left[\mathrm{Zn}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+}$ is 36, which matches Option C.