Question

Which of the following is isoelectronic of carbon?
A.$N{a^ + }$
B.$A{l^{3 + }}$
C.${O^{2 - }}$
D.${N^{^ + }}$

Answer 1

The elements or ions having the same number of electrons are called isoelectronic species. Isoelectronic species also have the same electronic configuration. To solve this question, we need to find the ion with the same number of electrons as carbon.

Complete step-by-step answer: The atomic number of carbon atoms is 6. So, its electronic configuration is $1{s^2}2{s^2}2{p^2}$. Hence the number of electrons in a carbon atom is also 6.
The atomic number of sodium atoms is 11. So, its electronic configuration is $1{s^2}2{s^2}2{p^6}3{s^1}$. In $N{a^ + }$ ion, one electron is removed from $3s$ orbital of the sodium atom. Hence electronic configuration of sodium ions is $1{s^2}2{s^2}2{p^6}$ and the total number of electrons in $N{a^ + }$ is 10.
The atomic number of aluminium atoms is 13. So, its electronic configuration is $1{s^2}2{s^2}2{p^6}3{s^2}3{p^1}$. In $A{l^{3 + }}$ ion, one electron is removed from $3p$ orbital and two electrons are removed from $3s$ orbital of aluminium atoms. Hence electronic configuration of aluminium ion is $1{s^2}2{s^2}2{p^6}$ and total number of electrons in $A{l^{3 + }}$ ion is 10.
The atomic number of oxygen atoms is 8. So, its electronic configuration is $1{s^2}2{s^2}2{p^4}$. In ${O^{2 - }}$ ion, two electrons are added to $2p$ orbital of the oxygen atom. Hence electronic configuration of oxygen ion is $1{s^2}2{s^2}2{p^6}$ and total number of electrons in ${O^{2 - }}$ ion is 10.
The atomic number of nitrogen atoms is 7. So, its electronic configuration is $1{s^2}2{s^2}2{p^3}$. In ${N^{^ + }}$ ion, one electron is removed from $2p$ orbital of the nitrogen atom. Hence electronic configuration of nitrogen ion is $1{s^2}2{s^2}2{p^2}$ and total number of electrons in ${N^{^ + }}$ ion is 6.
Therefore, ${N^{^ + }}$ is isoelectronic with a carbon atom as both have the same number of electrons which is 6 and the same electronic configuration.
Thus, the correct option is D.

Note: Atomic number is defined as the total number of electrons or protons in an atom.
When electrons are donated or gained by an atom, it gets a net positive or negative charge and is known as an ion. Ions with positive charge are known as cations and ions with negative charge are known as anions.