Question

How many unpaired electrons are in a low spin fe3+ complex high spin complex?

Answer 1

The terms used (high-spin and low-spin) doesn’t refer to a number of unpaired electrons but to different electron configuration in d-orbitals that you can get from the pairing energy. As for Fe3+’s unpaired electron here are the answers:

Octahedral high-spin: 5 unpaired electrons

Octahedral low-spin: 1 unpaired electron

Answer 2

The number of unpaired electrons in ${\text{F}}{{\text{e}}^{3 + }}$ for low spin and high spin complex is $\boxed1$ and $\boxed5$ respectively.

Further Explanation:

A coordination complex contains a central atom or ion mainly a transition metal surrounded by atoms or molecules containing lone pair of electrons or negative charges known as ligands. Ligands form coordinate bonds with vacant d orbitals of the metals by donating their electrons to metal atom or ion. The number of ligands attached to metal atom is known as the coordination number of the metal. Central atom and its ligands are enclosed in a square bracket called the coordination sphere with a formal charge outside on superscript in case of charged ligands. A coordination sphere generally can be represented as follows:

${\left[{{\text{M(L}}{{\text{)}}_{\text{x}}}}\right]^{\text{y}}}$

Where M is a central atom, L is a ligand, x is coordination number and y is the formal charge on the complex.

On the basis of their strength of splitting of d orbital of central metal, the ligands are classified as follows:

A. Strong ligands are those which cause larger splitting of the d orbital, hence pairing of electrons occurs in lower energy orbitals of d subshell.

B. Weak ligands are those which cause smaller splitting of the d orbital, hence instead of the pairing of electrons they make the transition to the high energy orbital of d subshell.  

On the basis of them, coordination complexes can be classified as low spin or high spin complexes.

1. Low spin complexes are those complexes in which strong ligands are present across the central metal. Example of low spin complexes is ${\left[ {{\text{Ni(CN}}{)_4}} \right]^{2 - }}$  

2. High spin complexes are those complexes in which weak ligands are present across the central metal. Example of high spin complex is ${\left[ {{\text{Co(}}{{\text{H}}_{\text{2}}}{\text{O}}{)_6}} \right]^{3 + }}$.

The electronic configuration of Fe is  $\left[ {{\text{Ar}}} \right]3{{\text{d}}^6}{\text{4}}{{\text{s}}^2}$

In ${\left[ {{\text{Fe(Ox}}{)_3}} \right]^{3 - }}$, Fe has a +3 oxidation state so its valence shell electronic configuration is $\left[ {{\text{Ar}}} \right]3{{\text{d}}^{\text{5}}}{\text{4}}{{\text{s}}^0}$.

${\text{F}}{{\text{e}}^{3 + }}$ in low spin will show pairing of electrons and it will result in one unpaired electron.  in high spin will show no pairing of electrons and it will result in five unpaired electrons. (Refer to the attached image)

Learn more:

1. The coordination number for lithium sulfide crystals: brainly.com/question/7558621

2. Determination of oxidation state of metal species: brainly.com/question/10017129

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Coordination compounds

Keywords: Coordination compound, [Fe(Ox)3]-3, Fe+3, pairing, unpaired, high spin, low, strong, and weak ligands.