Question

What is the difference between $F{e^{2 + }}$ and $F{e^{3 + }}$?

Answer 1

We know that Iron (Fe) is in the d-block of the periodic table. The atomic number is 26 which means that there are 26 electrons in the Iron atom. It can be represented by the following electronic configuration.
$1{s^2}\;2{s^2}\;2{p^6}\;3{s^2}\;3{p^6}\;4{s^2}\;3{d^6}$
Now we have two get $F{e^{2 + }}$ and $F{e^{3 + }}$ by removing electrons from this
For $F{e^{2 + }}$ we have to remove 2 electrons from the $4s$ orbital and for $F{e^{3 + }}$we have to remove 2 electrons from the $4s$ orbital and 1 electron from the $3d$ orbital.
This is one of the key factor that gives the different properties for $F{e^{2 + }}$ and $F{e^{3 + }}$

Complete answer:

| $F{e^{2 + }}$| $F{e^{3 + }}$
---|---|---
General characters| Fe loses 2 electrons from the valence shell and becomes $F{e^{2 + }}$ (+2 oxidation state)| Fe loses 3 electrons from the valence shell and becomes $F{e^{3 + }}$(+3 oxidation state)
Name| It is known as the ferrous ion| It is known as the ferric ion
Colour| Ferrous ions produce green colour in solutions and turns violet when added to waterE.g. $FeS{O_4}.{\text{ }}7{H_2}O$| Ferric ions produce yellow-brown colour in solutionE.g. $FeC{l_3}.{\text{ 6}}{H_2}O$
Magnetism| Usually, paramagnetic. However because there are an even number of electrons in Fe2+, it is possible that all of the electrons could end up as diamagnetic (low-spin complexes)| They can only be paramagnetic because there is always a lone electron
Electronic Configuration| $1{s^2}\;2{s^2}\;2{p^6}\;3{s^2}\;3{p^6}\;3{d^6}$| $1{s^2}\;2{s^2}\;2{p^6}\;3{s^2}\;3{p^6}\;3{d^5}$
Stability| $F{e^{2 + }}$ is not stable.| $F{e^{3 + }}$ ion is more stable due to its half-filled $3{d^5}$ electron configuration

Note:
Both $F{e^{2 + }}$ and $F{e^{3 + }}$ are the common oxidation states of Iron.
Ferrous Ion when kept for a long time can oxidise and therefore turn into ferric ions changing the colour and other properties.
Ferrous state ($F{e^{2 + }}$) iron acts as an electron donor, while in the ferric state ($F{e^{3 + }}$) it acts as an acceptor. They play important roles in our biological system like haemoglobin.