Question

Which of the following have an $\left( {18 + 2} \right)$ electron configuration?
This question has multiple correct options
A.$P{b^{2 + }}$
B.$C{d^{2 + }}$
C.$B{i^{3 + }}$
D.$S{O_4}^{2 - }$

Answer 1

Hint: We can say that electron configuration is the electron distribution of an atom (or) molecule found in atomic orbitals (or) molecular orbitals. We have to know that electronic configuration was devised from the Bohr model of the atom. We have to know that electronic configuration goes through standard notation where all electrons composed of atomic subshells are located in a particular order.

Complete answer:
We can write the electronic configuration of atoms using subshell labels of subshells. The labels have shell number, the name of the subshell, and the total amount of electrons in the subshell in superscript.
We have to know that $\left( {18 + 2} \right)$ electron configuration means there are eighteen electrons apart from the inner core electrons. So, let us now write the electronic configuration of the given ions.
$P{b^{2 + }}$ is an ion that is obtained when two electrons are lost from lead. We can write the electronic configuration of $P{b^{2 + }}$ as $\left[ {Xe} \right]4{f^{14}}5{d^{10}}6{s^2}$. This means that the first shell, second shell, third shell, and the fourth shell are completely filled whereas the fifth shell has eighteen electrons and the sixth shell has two electrons. So, Option (A) is correct.
$C{d^{2 + }}$ is an ion that is obtained when two electrons are lost from cadmium. We can write the electronic configuration of $C{d^{2 + }}$ as $\left[ {Kr} \right]4{d^{10}}$. This ion does not have $\left( {18 + 2} \right)$ electron configuration. So, Option (B) is incorrect.
$B{i^{3 + }}$ is an ion that is obtained when three electrons are lost from bismuth. We can write the electronic configuration of $B{i^{3 + }}$ as $\left[ {Xe} \right]4{f^{14}}5{d^{10}}6{s^2}$. This means that the first shell, second shell, third shell, and the fourth shell are completely filled whereas the fifth shell has eighteen electrons and the sixth shell has two electrons. So, Option (B) is correct.
$S{O_4}^{2 - }$ is a polyatomic ion and it does not have $\left( {18 + 2} \right)$ electron configuration. So, Option (D) is incorrect.
So, the ions that contain $\left( {18 + 2} \right)$ electron configuration are $P{b^{2 + }}$ and $B{i^{3 + }}$.

Option (A) and (C) are correct.

Note:
We have to know that with the help of electronic configurations we can determine the valency of an element; we can predict the properties of elements that are in a particular group which means elements that exhibit similar electron configurations would exhibit properties. We can also interpret the atomic spectra.