Question

Aluminium atom has ground state electronic configuration as:
A.$1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^1}$
B.$1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^6}3{{\text{s}}^1}$
C.$1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^6}3{{\text{s}}^2}3{{\text{p}}^1}$
D.$1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^6}3{{\text{s}}^2}3{{\text{p}}^1}3{{\text{p}}^{12}}$
E.$1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^6}3{{\text{s}}^2}3{{\text{p}}^1}3{{\text{p}}^{12}}4{{\text{p}}^6}$

Answer 1

we must have the knowledge of writing electronic configuration for the element following the required law for filling of electrons in an orbital. Electrons are filled in a particular order in a defined set of orbits.

Complete step by step solution:
Electronic configuration is defined when electrons are classified in atomic orbitals. It is useful for determining the valency of the element and helps in predicting the properties along a group and period. There are different shells present in an atom. Within the shell there are various subshells and in subshell different orbitals are present within which electrons are filled.
The order of filling of electrons following Aufbau principle as follow:
$1{\text{s }}2{\text{s }}2{\text{p }}3{\text{s }}3{\text{p 4s 3d 4p}}...$
Pauli Exclusion Principle says that a maximum of two electrons can be filled in a particular orbital that too with opposite spins.
s subshell has one orbital so it can have a maximum of 2 electrons. p subshell has 3 orbital and can have a maximum of 6 electrons and d subshell, hence 5 electrons and can accommodate a maximum of 10 electrons.
Aluminium has an atomic number of 13. So we will fill these electrons in keeping in mind the above property and hence the electronic configuration will be:
$1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^6}3{{\text{s}}^2}3{{\text{p}}^1}$. We will calculate the total number of electrons$2 + 2 + 6 + 2 + 1 = 13$.
Hence, the electronic configuration of aluminium is $1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^6}3{{\text{s}}^2}3{{\text{p}}^1}$ and the correct option is C.

Note: As we see the last electron of aluminium goes to the p subshell and hence it is a p block element. The group number of aluminium is 13 and the period number is 3. It is a trivalent species and donated 2 electrons to form tripositive ions and hence is metallic in nature.