Question

The mass number of a particular element which has equal number of protons and neutrons is $32$. What is the electronic configuration of the atom and its stable ion?

Answer 1

1. The mass number $\left(A\right)$ of an atom is calculated by adding the number of protons and neutrons.
2. The nucleus of an atom contains both protons and neutrons, which are referred to as nucleons.
3. While the number of protons in each atom of an element remains constant, the number of neutrons might fluctuate.
4. As a result, various isotopes of the same element can have different mass values.
5. An electron's mass is almost insignificant. As a result, an atom's atomic mass is nearly equal to its mass number
6. Given: Mass Number = $32$

According to the question, $No.ofprotons\left(p\right)=No.ofneutrons\left(n\right)$

$$\begin{gathered} No.ofprotons\left(p\right)+No.ofneutrons\left(n\right)=32 \\ p+p=32 \\ 2p=32 \\ \Rightarrow p=16 \end{gathered}$$

Thus, the atomic number of the element having a mass number $32$ is $16$.

7. Hence, the element is sulphur having an electronic configuration = $2,8,6$.

8. $S^{-2}$ is the stable ion of sulphur because it only requires two electrons to complete its octet.

9. Thus, its stable ion's electronic configuration is $2,8,8$.