Question

Write electronic configurations of Fe, ${\text{F}}{{\text{e}}^{{\text{2 +
}}}}$,$\,{\text{F}}{{\text{e}}^{{\text{3 + }}}}$

Answer 1

Hint: We will determine the atomic number and write the electronic configuration of Fe metal. The superscript on the representation of the element symbol tells the oxidation number of the element. The oxidation number of an element tells the number of electrons gained or lost. The positive charge shows the loss of electrons. The negative charge shows the gain of electrons.

Complete step by step solution:The Fe metal belongs to the d-block. The electronic configuration of the d-block element is, $\left( {{\text{n}} - 1} \right){{\text{d}}^{1 - 10}}{\text{ns}}$.
It is a third period and eight group element. So, the outermost shell of Fe will be${\text{3d}}\,{\text{4s}}$ and the valence electron will be eight.
The atomic number of iron is $26$.
So, the electronic configuration of Fe is as follows:

${\text{1}}{{\text{s}}^{\text{2}}}{\text{2}}{{\text{s}}^{\text{2}}}{\text{2}}{{\text{p}}^{\text{6}}}{\text{3}}{{\text{s}}^{\text{2}}}{\text{3}}{{\text{p}}^{\text{6}}}{\text{3}}{{\text{d}}^{\text{6}}}{\text{4}}{{\text{s}}^{\text{2}}}$
Fe is a neutral atom. The oxidation number of Fe in ${\text{F}}{{\text{e}}^{{\text{2 + }}}}$is $ + 2$ it means Fe loses two electrons. When it loses two electrons it forms${\text{F}}{{\text{e}}^{{\text{2 + }}}}$.
So, the electronic configuration of ${\text{F}}{{\text{e}}^{{\text{2 + }}}}$is as follows:
${\text{1}}{{\text{s}}^{\text{2}}}{\text{2}}{{\text{s}}^{\text{2}}}{\text{2}}{{\text{p}}^{\text{6}}}{\text{3}}{{\text{s}}^{\text{2}}}{\text{3}}{{\text{p}}^{\text{6}}}{\text{3}}{{\text{d}}^{\text{6}}}$
The oxidation number of Fe in $\,{\text{F}}{{\text{e}}^{{\text{3 + }}}}$is $ + 3$ it means Fe loses three electrons. When Fe loses three electrons it forms$\,{\text{F}}{{\text{e}}^{{\text{3 + }}}}$.
So, the electronic configuration of $\,{\text{F}}{{\text{e}}^{{\text{3 + }}}}$is as follows:
${\text{1}}{{\text{s}}^{\text{2}}}{\text{2}}{{\text{s}}^{\text{2}}}{\text{2}}{{\text{p}}^{\text{6}}}{\text{3}}{{\text{s}}^{\text{2}}}{\text{3}}{{\text{p}}^{\text{6}}}{\text{3}}{{\text{d}}^5}$

Note: Block tells the outermost orbitals of the element and also tells the general configuration. The period number tells the principal quantum number of the outermost shell. Group number indicates the electrons present in the outermost valence shell. The group number can also be represented in roman numbers. S and P-block are represented by ‘A’ and the d-block is represented by ‘B’. The subscript on the representation of the element symbol tells the number of atoms.