Question

Maximum number of unpaired electrons are present in?
A.$$T{i}^{+2}$$
B.$$S{c}^{+3}$$
C.$$C{r}^{+3}$$
D.$$M{n}^{+2}$$

Answer 1

Hint: The filling of electrons in different orbitals of the atoms are governed by few rules. These rules determine the concept like which energy orbital is to be filled first than other and in which manner. These rules are like the ‘Aufbau principle and Hund’s rule, Pauli exclusion principle’.

Complete answer:
As we know that these above different rules govern the filling of the orbital, so first let’s have a quick look at these laws for a better understanding of the question.
So, the Aufbau principle states that the lowest energy orbital is filled first, followed by the orbitals of continuously increasing energy.
And according to the Hund's rules- it states that where orbitals are of equal energy each has one electron before any have two electrons. This means that first the orbital of equal energy is half- filled, then the second electron starts filling in the orbital to make it completely filled.
Now let’s have a look at the atoms or ions given in question:
So, to answer these we need to know the atomic number and the electronic configuration of these atoms:
So, let’s see: electronic configuration of these ions are as following:
$$\begin{gathered} T{i}^{+2}-\left[Ar\right]3d^2 \\ S{c}^{+3}-\left[Ar\right] \\ C{r}^{+3}-\left[Ar\right]3d^3 \\ M{n}^{+2}-\left[Ar\right]3d^5 \end{gathered}$$
So, as we can see the EC of these atoms, the maximum number of unpaired electrons are present in $$M{n}^{+2}$$ , it is half-filled orbital and has $$5$$ unpaired electrons.

So, from the above discussion we can say that the correct option is D i.e. $$M{n}^{+2}$$

Note:
Here, always keep in mind while calculating the number of unpaired electrons or electrons, that the atom is neutral or is an ion i.e. whether a given element is in the neutral form or an anion or cation.