How do you write shorthand notations for elements?

Hint:. The answer for this question lies in the basic concept of chemistry where the shorthand notations are nothing but writing the electronic configuration of an atom which is preceded by the noble gas configuration.

Complete step by step answer:
- In the lower classes of chemistry, we have studied the writing of the electronic configuration of an element which is based on the atomic number of an element.
Now, we shall study in detail about the shorthand notations given for only several elements.
- Shorthand notation is the notation which uses the noble gas of the previous line.
- The configuration is written in this way because all the orbitals up to that particular noble gas are completely filled and then the remaining orbitals are filled for the element for the row that it is present in.
- We can understand this concept if we consider a simple example of one element as magnesium which has the atomic symbol $Mg$ and atomic number 12 with the complete electronic configuration of $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}$
- Now, since the noble gas configuration which is near to this configuration is neon that is $Ne$ with atomic number 10 and the configuration $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}$ which is the completely filled orbital, we can write the configuration of magnesium in the shorthand notation as $[Ne]3{{s}^{2}}$
This way we can write the shorthand notations of the several elements.

Note: Note that shorthand notations can be written for the elements coming after neon because neon comes first in the noble gas which has completely filled electrons in its shell and these noble gas symbols are to be written in the square brackets.