Question

Write the electronic configuration of the Boron.

Answer 1

Boron belongs to the group no. 13 and it’s atomic no. is 5. So, it has 5 electrons. General valence electronic configuration of group 13 elements is $n{s^2}n{p^1}$. To write the electronic configuration of boron, fill its 5 electrons in the orbitals arranged in order of increasing energies, according to Aufbau Principle.

Complete step by step solution:
An electron in an atom is characterised by 4 quantum numbers, and the principal quantum number $(n)$ defines the main energy level known as the shell. Each shell consists of one or more subshells or sub-levels. Each subshell is assigned by azimuthal quantum no. ($l$) and $l$have values from 0 to $n - 1$ Also, each subshell has orbitals equal to $2l + 1$ . The distribution of electrons into orbitals of an atom is called its electronic configuration.
Boron has atomic no. 5 and it is represented by symbol the B. It belongs to group 13 of p-block. Group 13 elements outermost or valence electronic configuration is $\left[ E \right]n{s^2}n{p^1}$, where E is an inert gas configuration).
To find the electronic configuration of boron, fill 5 electrons of boron in orbitals according to Aufbau principle. Consequently, electronic configuration of boron will be :$1{s^2}2{s^2}2{p^1}$.
Now, to write the noble gas electronic configuration of boron, we need to find the noble gas that comes before boron in the periodic table and it is helium ( electronic configuration of helium is $1{s^2}$).
Therefore, the noble gas electronic configuration of boron is $\left[ {He} \right]2{s^2}2{p^1}$. The 2 in $2{s^2}and\,2{p^2}$ denotes the shell no (n) and shell number denotes the period no. to which the element belongs. Thus, boron belongs to period 2 of the periodic table.

Note: The orbital picture of boron can be represented as :
$s$- orbital can hold up maximum 2 electrons, $p$-orbitals can hold maximum 6 electrons.