Final answer:
The pair with the maximum difference in the value of spin-only magnetic moment is B. Pd²⁺, V²⁺. Option number b is correct.
Step-by-step explanation:
The species with the maximum difference in the value of spin-only magnetic moment would be one with the highest number of unpaired electrons. Unpaired electrons contribute to a higher magnetic moment. So, in the given pairs:
A. Fe³⁺, Mn²⁺: Fe³⁺ has 5 unpaired electrons, while Mn²⁺ has 5 unpaired electrons. Both have the same number of unpaired electrons, so the difference is zero.
B. Pd²⁺, V²⁺: Pd²⁺ has no unpaired electrons, while V²⁺ has 3 unpaired electrons. Therefore, Pd²⁺ has a lower magnetic moment compared to V²⁺.
C. Mn³⁺, Mn²⁺: Mn³⁺ has 4 unpaired electrons, while Mn²⁺ has 5 unpaired electrons. Therefore, Mn²⁺ has a higher magnetic moment compared to Mn³⁺.
Based on this, the pair with the maximum difference in the value of spin-only magnetic moment is B. Pd²⁺, V²⁺.