The complex ion Fe(CN)6 ^3- is paramagnetic with one...

The complex ion $\mathrm{Fe}(\mathrm{CN})_{6}{ }^{3-}$ is paramagnetic with one unpaired electron. The complex ion $\mathrm{Fe}(\mathrm{SCN})_{6}{ }^{3-}$ has five unpaired electrons. Where does $\mathrm{SCN}^{-}$ lie in the spectrochemical series relative to $\mathrm{CN}^{-}$ ?

Key Concepts

Ligand Field Strength

Ligand field strength refers to the ability of a ligand to produce a strong electrostatic field around the metal ion, leading to significant splitting of its d orbitals. Strong-field ligands, such as cyanide (CN?), favor low-spin configurations by causing large splitting, whereas weak-field ligands, like thiocyanate (SCN?) in this context, produce smaller splitting and typically result in high-spin complexes.

Paramagnetism

Paramagnetism in coordination compounds arises from the presence of unpaired electrons, which create magnetic moments that align with an external magnetic field. The magnetic behavior of a complex (whether it is high-spin with many unpaired electrons or low-spin with few unpaired electrons) is directly influenced by the ligand field strength and the corresponding electron distribution in the metal's d orbitals.

Spectrochemical Series

The spectrochemical series is a ranking of ligands based on the magnitude of the crystal field splitting (?) they induce in the d orbitals of a central metal ion. Ligands at the high field end produce large splitting and often lead to low-spin configurations, whereas those at the low field end cause smaller splitting, which favors high-spin configurations. This ordering helps predict magnetic and spectroscopic properties of coordination complexes.

Crystal Field Theory

Crystal field theory explains how the degeneracy of the d orbitals in a transition metal ion is lifted when ligands surround the metal center. The resulting energy gap between the split orbitals depends on the strength of the ligand's electric field and determines whether electrons will pair in the lower energy orbitals (leading to low-spin complexes) or occupy higher energy orbitals unpaired (leading to high-spin complexes).

Transcript

00:01 Here the question is the complex ion fe cn6 3 negative is paramagnitive with one unpaired electron.

00:11 The complex ion fe scn6 3 negative has 5 unpaired electrons.

00:19 Where does scn minus lie in spectrochemical series relative to cn minus? so looking to this first complex is given that is f .e .c .n .6.

00:48 F .e.

00:50 C .n .6.

00:54 3 negative.

00:57 Here f .e is the central metal atom and its outer electronic configuration after er, it is 4s2 3d6.

01:16 Fe is here at plus 3 oxidation state.

01:23 So its configuration will be 4s0 3d5.

01:37 Now we have to look at the nature of the ligand.

01:41 Ligand is c .n.

01:47 Which is very strong ligand.

01:53 And because of that, crystal field splitting energy is very large.

02:01 That means the energy difference between upper and lower is very large lower lower orbitals is very large this is crystal field splitting energy which is represented by this delta and these are lower energy levels these are higher energy levels and electronic configuration will be when it is large first lower levels are filled and then only upper levels so 5 electrons we have to fill in d orbitals so here it should be 1 2 3 4 5 and that is how one unpaired electron is left which is responsible for the paramagnetal property of the complex...

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