In which of the following compounds manganese show maximum radius ?

Question

Accepted Answer

In the given question, we are asked to determine in which compound manganese exhibits the maximum radius. The correct answer is Option 3: MnO. Let's explore why this is the case and why the other options are incorrect.

1. **Explanation for Option 3 (MnO):**
   - In MnO, manganese is in the +2 oxidation state (Mn²⁺). The ionic radius of an ion generally increases as the positive charge decreases because there are fewer protons to pull the electron cloud closer to the nucleus. In the +2 oxidation state, manganese has lost two electrons, resulting in a relatively larger ionic radius compared to higher oxidation states. Therefore, MnO, where manganese is in the +2 state, will have the largest ionic radius among the given options.

2. **Explanation for why other options are incorrect:**

- **Option 1 ($MnO_{2}$):**
     - In $MnO_{2}$, manganese is in the +4 oxidation state (Mn⁴⁺). The higher positive charge results in a smaller ionic radius due to the increased effective nuclear charge, which pulls the electrons closer to the nucleus. Therefore, the ionic radius of manganese in $MnO_{2}$ is smaller than in MnO.

- **Option 2 ($KMnO_{4}$):**
     - In $KMnO_{4}$, manganese is in the +7 oxidation state (Mn⁷⁺). This is the highest oxidation state for manganese, leading to a very small ionic radius because the high positive charge significantly increases the effective nuclear charge, pulling the electrons even closer to the nucleus. Thus, the ionic radius of manganese in $KMnO_{4}$ is much smaller than in MnO.

- **Option 4 ($K_{3}[Mn(CN)_{6}]$):**
     - In $K_{3}[Mn(CN)_{6}]$, manganese is typically in the +3 oxidation state (Mn³⁺). While this is lower than the +4 and +7 states, it is still higher than the +2 state in MnO. Consequently, the ionic radius of manganese in $K_{3}[Mn(CN)_{6}]$ is smaller than in MnO due to the greater effective nuclear charge compared to Mn²⁺.

In conclusion, MnO, where manganese is in the +2 oxidation state, has the largest ionic radius among the given compounds. This is because the lower positive charge results in a less effective nuclear pull on the electron cloud, allowing the radius to be larger compared to the higher oxidation states in the other compounds.