Answer: Option (D) is the correct answer.
Step-by-step explanation:
When an atom gains an electron then it becomes negatively charged due to the increase in number of electrons. Whereas when an atom loses an electron then it becomes positively charged due to the decrease in number of electrons.
The electronic configuration of sodium is
.
The electronic configuration of chlorine is
.
Sodium atom has one extra electron in its valence shell whereas chlorine has short of 1 electron to fill its valence shell. Therefore, chlorine will accept one electron from sodium atom and will act as an anion.
Thus, we can conclude that chlorine becomes an anion by gaining an electron from sodium.