Write condensed orbital notation of electronic configuration of the following elements:
a. Lithium (Z = 3)
b. Carbon (Z = 6)
c. Oxygen (Z = 8)
d. Silicon (Z = 14)
e. Chlorine (Z = 17)
f. Calcium (Z = 20)

Hint: In order to write condensed orbital notation of electronic configuration of the given elements, we must know how the electrons are filled in the atomic orbitals and how the subshells are arranged. The electrons are arranged in the subshell according to Aufbau's principle.

Complete Solution :
Each electron present in an atom is present in a subshell. There are totally four subshells present which are labelled as s, p, d and f. Each subshell can accommodate only a certain number of electrons, i.e. only 2 electrons can be occupied in s subshell, 6 electrons in p subshell, 10 electrons in d subshell and 14 electrons in f subshell.
- We can write the electronic configuration of an atom by assigning the number of electrons that are present in the atom as the superscript of the subshell. These electrons are filled in the subshells according to the Aufbau’s principle. We can also write the electronic configuration of an element by using the noble gases. These noble gases have stable configuration i.e. completely filled outermost orbitals. So, these noble gases can be prefixed in the outermost shell of the element whose electronic configuration is being calculated.

Therefore, The electronic configuration of
a. Lithium (Z=3) = \[1{s^2}2{s^1}\]
b. Carbon (Z=6) = \[1{s^2}2{s^2}2{p^2}\]
c. Oxygen (Z=8) = \[1{s^2}2{s^2}2{p^4}\]
d. Silicon (Z=14) = \[1{s^2}2{s^2}2{p^6}3{s^2}3{p^2}\]= \[[Ne]3{s^2}3{p^2}\]
e. Chlorine (Z=17) = \[1{s^2}2{s^2}2{p^6}3{s^2}3{p^5} = [Ne]3{s^2}3{p^5}\]
f. Calcium (Z=20) = \[1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2} = [Ar]4{s^2}\]

Additional Information. The Aufbau’s principle was formulated by two scientists namely Wolfgang Pauli and Niels Bohr in the early 1920’s. The principle was not named after a scientist, but the name came from German, Aufbauprinzip, which means building-up principle.

Note: Not only Aufbau’s principles are followed to fill the electrons in the orbitals, but also other principles have been to arrange the electrons. They are
- Hund’s Rule:
Every orbital in a subshell should be singly filled before any of the orbitals are doubly filled. Each singly filled orbital should have the same spin.
- Pauli’s exclusion principle:
No two electrons in an atom can have all four quantum numbers identical.