Which of the following properties are related to the complex $[Fe(H_2O)_6]^{3+}$?
(A) Paramagnetic
(B) number of unpaired electrons are five
(C) $d^2sp^3$ hybridisation
(D) $H_2O$ is a strong field ligand
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A) and (B) only
In complexes, magnetic behavior depends on unpaired d-electrons.
$\text{H}_2\text{O}$ is a weak field ligand in the spectrochemical series.
$\text{Fe}^{3+} \rightarrow$ atomic number $26 \rightarrow \text{Fe}^{3+} = \mathbf{3d^5}$ configuration.
Metal Ion:
$Fe^{3+} \rightarrow \text{remove 3 electrons from } Fe \rightarrow \mathbf{3d^5}$
Ligand Strength:
$H_2O$ is a weak field ligand, so it forms a high-spin complex.
Electron Arrangement (Octahedral Field):
$t_{2g}^3 \, e_g^2 \rightarrow \mathbf{5 \text{ unpaired electrons}}$
Option-wise Explanation
(A) Paramagnetic
True. Presence of unpaired electrons causes paramagnetism. Here we have 5 unpaired electrons.
(B) Number of unpaired electrons are five
True. High-spin $d^5$ configuration gives one electron in each d orbital.
(C) $d^2sp^3$ Hybridisation
False. Weak field ligands cause outer orbital complex $\rightarrow \mathbf{sp^3d^2}$ hybridisation, not $d^2sp^3$.
(D) $H_2O$ is a strong field ligand
False. $H_2O$ lies in the middle of spectrochemical series and behaves as weak field.