Question

Write the chemical formula of sodium chloride.

Answer 1

Hint: Think about the names and the associated symbols of the elements involved in the making of this compound. Consider the valency of both the elements before writing the chemical formula.

Complete step by step answer:
It has been given that the elements involved in the composition of sodium chloride are: the metal sodium and the halogen chlorine. The chemical symbols for both these elements are $Na$ for sodium and $Cl$ for chlorine. So, the chemical composition of sodium chloride will consist of these two elements in a specific proportion.
Now let us look at the atomic numbers and the associated valency of the elements to determine the proportion. We know that the atomic number of sodium is 11 and that of chlorine is 17.

From this, we can infer that sodium needs to lose one electron to achieve a stable octet since the electronic configuration is 2, 8, 1. Chlorine needs to accept one electron to achieve a stable octet since the electronic configuration is 2, 8, 7.
So, we can say that the outermost electron of sodium will be donated to the outermost shell of one chlorine atom. Thus, one sodium atom is enough to satisfy the valency of one chlorine atom and vice versa.
Hence, the chemical formula of sodium chloride will be $NaCl$.

Note: Remember that although the third orbital has a total capacity of 18 electrons, it has three sub-orbitals with the capacities 2, 6, and 10. In the third period, only the first two sub-orbitals are filled, and the third sub-orbital is filled in the fourth period. Refer to the Aufbau principle for further insight.