Question

How will you find the valency of sodium, chlorine, and argon?

Answer 1

As we know that each element in the universe wants to be in its stable state. To get stable states, elements complete their octet. To complete their octet, each element or substance loses or gains electrons according to their requirement.

Complete step by step answer:
Before finding the valency of the given element. Let's have a look at valency.
Valency: It is the combining capacity of an atom with another element's atom or the number of electrons it gains or loses to complete its octet it is known as valency.
To find the valency, atomic numbers play a very important role.
Well, electron configuration plays a major role in identifying the valency of the atom, in which electrons distribute in shells $K, L, M, N$ in the pattern of $2,8,18,32$.
The electronic configuration is described according to the Bohr Model, and it is based on the principle of quantum number.
Now, find the valency of the following elements sodium, chlorine, and argon.
Sodium, its atomic number is $11$. According to the electronic configuration pattern, it distributes like, $2,8,1$.
So, there is $1$ electron in its outermost shell and to complete it we need $7$ more electrons. Therefore, instead, gain $7$ electron, it loses $1$ and becomes stable. Because gaining $7$ electron needed high energy rather than lose $1$ .
Now, we got the valency of sodium that is $1$.
Chlorine, its atomic number is $17$ and its configuration is $2,8,7$. So, there is $7$ electron in its outermost shell and to complete it we need $1$ more electron. Therefore, it gains $1$ electron from another element.
Now, we got the valency of Chlorine is $1$.
Argon, its atomic number is $18$ and its electronic configuration is $2,8,8$. So, what we have seen here is that there is no need to complete shells because they are already completed. Therefore, the valency of Argon is $0$.

Note:
Atomic number- The number of protons present in the nucleus is known as the atomic number. Its symbol is $Z$. Bohr Model- In $1915$ Neil Bohr proposed a Bohr model. It describes the atomic structure, energy level of each shell.
That element has $0$ valency as Argon is considered a noble gas. All elements from a group $18$ are the noble gas element.