NEETChemistryClassification of Elements and Periodicity in Properties
The sum of the first two ionisation enthalpies (IE₁ + IE₂) for nickel (Ni) is less than that for platinum (Pt). However, the sum of the first four ionisation enthalpies (IE₁ + IE₂ + IE₃ + IE₄) for platinum is less than that for nickel. Based on this data, which of the following statements regarding the thermodynamic stability of their compounds is correct?
Options
- APt ²⁺ compounds are more stable than Ni ²⁺ compounds, and Ni ⁴⁺ compounds are more stable than Pt ⁴⁺ compounds
- BBoth Ni ²⁺ and Ni ⁴⁺ compounds are more stable than the corresponding platinum compounds.
- CBoth Pt ²⁺ and Pt ⁴⁺ compounds are more stable than the corresponding nickel compounds.
- DNi ²⁺ compounds are more stable than Pt ²⁺ compounds, and Pt ⁴⁺ compounds are more stable than Ni ⁴⁺ compounds
Correct answer
D. Ni ²⁺ compounds are more stable than Pt ²⁺ compounds, and Pt ⁴⁺ compounds are more stable than Ni ⁴⁺ compounds
Step-by-step solution
The thermodynamic stability of a particular oxidation state of a transition metal can be evaluated using the sum of the relevant ionisation enthalpies. A lower sum of ionisation enthalpies implies that less energy is required to reach that oxidation state, resulting in higher thermodynamic stability. Since the sum of the first two ionisation enthalpies (IE₁ + IE₂) for Ni is less than that for Pt, it requires less energy to form Ni ²⁺ compared to Pt ²⁺ . Thus, Ni ²⁺ compounds are thermodynamically more stable than P