Question

Select outer d-complexes :

$I:\left[Fe\right(CN{)}_6{]}^{3-}II:\left[Fe\right(H_{2}O{)}_6{]}^{2+}$

$III:[Co{F}_6{]}^{3-}$

• A. II, III
• B. I, II
• C. I, III
• D. I, II, III

Answer 1

The correct option is A II, III

Outer orbital complexes involve the use of the s- and p-orbitals of one energy level and the d-orbitals on the same energy level.
${Fe}^{2+}$ uses the 4s, 4p, and 4d orbitals to bind the six water molecules.
Similar is the case with ${Co}^{3+}$ whose configuration is $\left[Ar\right]3d^6$. Their reasoning is that the 4s energy orbital is higher than the 3d orbital and thus they are removed first. "The stability of half-filled subshells may be tempting ($\left[Ar\right]4s^1,3d^5$), but this is a less favorable configuration due to higher energy of the 4s orbital".