Question

How many unpaired electrons are present in \[M{n^{2 + }}\] ion?

Answer 1

Hint: An unpaired electron is a single electron that occupies an atom's orbital rather than as part of a pair of electrons. An atom's atomic orbitals have the ability to hold two electrons with opposite spins.

Complete answer:
The total number of electrons in a neutral element is represented by its electronic configuration. To find the number of electrons in an atom, we should add all the superscripts together. We know that the electrons are filled in order of increasing energies according to Aufbau's law.
So, the electronic configuration of Mn is: 25
that is, \[1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}3{d^5}4{s^2}\]
Also the electronic configuration of \[M{n^{2 + }}\] is, 23
that is, \[1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}3{d^5}\]
We know that each of an atom's atomic orbitals (defined by the three quantum numbers n, l, and m) can hold a maximum of two electrons with opposite spins, known as an electron pair.
Here, since electrons can only have a pair until any orbital in "degenerate" has been singly filled; there are five orbitals in the 3d subshell, each containing two electrons.
Hence, there is just one electron in each orbital.
As there are five 3d orbitals here, each orbital has a single electron.
Hence, \[M{n^{2 + }}\] has 5 unpaired electrons.
Hence, there are five unpaired electrons in \[M{n^{2 + }}\].

Note:
Remember the Aufbau principle which is also known as the Aufbauprinzip (building-up principle), states that in the ground state of an atom or ion, electrons fill atomic orbitals of the lowest possible energy levels before moving on to higher levels.