Question

What would be the electronic configuration of ${\mathrm{Na}}^{+}$, ${\mathrm{Al}}^{3+}$, ${\mathrm{O}}^{2-}$and ${\mathrm{Cl}}^{-}$.

Answer 1

Electronic configuration:

1. The distribution of electrons in various energy levels or shells of an atom of the element is known as its electronic configuration.
2. Starting from the nucleus, the shells are named as $\mathrm{K},\mathrm{L},\mathrm{M},\mathrm{N},$….. and so on.
3. The capacity of $\mathrm{K}$ shell is to hold maximum $2$ electrons, that of $\mathrm{L}$ shell is to hold $8$ electrons, that of $\mathrm{M}$ shell is to hold $18$ electrons and that of $\mathrm{N}$ shell is to hold $32$ electrons.

Electronic configuration of ${\mathrm{Na}}^{+}$:

1. The atomic number of Sodium $\left(\mathrm{Na}\right)$ is $11$. Thus, Sodium atom has $11$ electrons.
2. One positive charge on ${\mathrm{Na}}^{+}$ indicates that ${\mathrm{Na}}^{+}$ ion is formed when Sodium atom loses one electron.
3. Thus, ${\mathrm{Na}}^{+}$ ion has $11-1=10$ electrons.
4. In the electronic configuration of ${\mathrm{Na}}^{+}$ ion, $2$ electrons accommodate in the $\mathrm{K}$ shell and the remaining $8$ electrons accommodate in the $\mathrm{L}$ shell.
5. Thus, the electronic configuration of ${\mathrm{Na}}^{+}$ is $(2,8)$.

Electronic configuration of ${\mathrm{Al}}^{3+}$:

1. The atomic number of Aluminium $\left(\mathrm{Al}\right)$ is $13$. Thus, Aluminium atom has $13$ electrons.
2. Three positive charges on ${\mathrm{Al}}^{3+}$ indicates that ${\mathrm{Al}}^{3+}$ ion is formed when Aluminium atom loses three electrons.
3. Thus, ${\mathrm{Al}}^{3+}$ ion has $13-3=10$ electrons.
4. In the electronic configuration of ${\mathrm{Al}}^{3+}$ ion, $2$ electrons accommodate in the $\mathrm{K}$ shell and the remaining $8$ electrons accommodate in the $\mathrm{L}$ shell.
5. Thus, the electronic configuration of ${\mathrm{Al}}^{3+}$ is $(2,8)$.

Electronic configuration of ${\mathrm{O}}^{2-}$:

1. The atomic number of Oxygen $\left(O\right)$ is $8$. Thus, Oxygen atom has $8$ electrons.
2. Two negative charges on ${\mathrm{O}}^{2-}$ indicates that ${\mathrm{O}}^{2-}$ ion is formed when Oxygen atom gains two electrons.
3. Thus, ${\mathrm{O}}^{2-}$ ion has $8+2=10$ electrons.
4. In the electronic configuration of ${\mathrm{O}}^{2-}$ ion, $2$ electrons accommodate in the $\mathrm{K}$ shell and the remaining $8$ electrons accommodate in the $\mathrm{L}$ shell.
5. Thus, the electronic configuration of ${\mathrm{O}}^{2-}$ is $(2,8)$.

Electronic configuration of ${\mathrm{Cl}}^{-}$:

1. The atomic number of Chlorine $\left(\mathrm{Cl}\right)$ is $17$. Thus, Chlorine atom has $17$ electrons.
2. One negative charge on ${\mathrm{Cl}}^{-}$ indicates that ${\mathrm{Cl}}^{-}$ ion is formed when Chlorine atom gains one electron.
3. Thus, ${\mathrm{Cl}}^{-}$ ion has $17+1=18$ electrons.
4. In the electronic configuration of ${\mathrm{Cl}}^{-}$ ion, $2$ electrons accommodate in the $\mathrm{K}$ shell, $8$ electrons accommodate in the $\mathrm{L}$ shell and the remaining $8$ electrons accommodate in the $\mathrm{M}$ shell.
5. Thus, the electronic configuration of ${\mathrm{Cl}}^{-}$ is $(2,8,8)$

Thus, the electronic configurations of ${\mathrm{Na}}^{+}$, ${\mathrm{Al}}^{3+}$, ${\mathrm{O}}^{2-}$and ${\mathrm{Cl}}^{-}$are $(2,8)$, $(2,8)$, $(2,8)$ and $(2,8,8)$ respectively.