Question

Which has the greater octahedral field splitting energy? (Δo)

[Cr(H2O)6]2+ or [Cr(H2O)6]3+ Blank 1. Fill in the blank, read surrounding text.

[Fe(NO2)6]3- or [FeCl6]3- Blank 2. Fill in the blank, read surrounding text.

(Please Note: There was typo that was corrected in the formula. If you answered using either [Fe(NO2)6]2+ or [Fe(Cl6)6]2+ and were correct, you will still receive full credit).

Na4[V(CN)4(OH)2] or Na4[Ta(CN)4(OH)2]

Answer 1

• [Cr(H2O)6]3+ will have greater splitting energy in comparison to [Cr(H2O)6]2+ because the charge on the central metal atom (Cr) is +3 in  [Cr(H2O)6]3+ and +2 in [Cr(H2O)6]2+. Greater the value of charge on central metal atom greater will be the octahedral splitting energy.
• In both [Fe(NO2)6]3- and [FeCl6]3-, the ceentral metal (Fe) have same charge (+3). We can compare the splitting energy on the basis of strenght of ligand. NO₂^- is a strong feild ligand in comparison to Cl^- , so it results in more splitting. Therefore [Fe(NO2)6]3- have a higher splitting energy value.
• In case of Na4[V(CN)4(OH)2] and Na4[Ta(CN)4(OH)2] the ligands and the charge on central metal atom are same. We can compare the splitting energy values on the basis of group property. As we go down the group splitting energy increases specially if the ligands are π-donors such as CN^-. Ta is 5d- series metal whereas V is 3d- series metal, therefore,Na4[Ta(CN)4(OH)2] will have greater splitting energy.