Question

Using noble gas shorthand, write the electronic configuration for $Pu$?

Answer 1

Noble gas shorthand is a method of expressing electronic configuration of any noble gas by using any other noble gas in its configuration. It is also known as a short version for writing electronic configuration by using noble gas to represent the complete atomic orbital of any other atom.

Complete answer:
There are a large number of elements present in the periodic table and having high atomic number values. In that case when we write the complete electronic configuration of that element it becomes so lengthy. In order to write the electronic configuration of elements in a short and precise manner we use the noble gas shorthand method.
In case of plutonium $Pu$, atomic number of elements is $94$ so if we write entire electronic configuration it will be-
$1{s^2}2{s^2}2{p^6}3{s^2}4{s^2}3{d^{10}}4{p^6}5{s^2}4{d^{10}}5{p^6}6{s^2}4{f^{14}}5{d^{10}}6{p^6}7{s^2}5{f^6}$
As we see this is very lengthy so we use any noble gas which has an atomic number less than plutonium. Hence the noble gas has a segment of electronic configuration similar with the plutonium like atomic number of Radon is $86$, so its electronic configuration will be-
$1{s^2}2{s^2}2{p^6}3{s^2}4{s^2}3{d^{10}}4{p^6}5{s^2}4{d^{10}}5{p^6}6{s^2}4{f^{14}}5{d^{10}}6{p^6}$
From the above configuration we see that, upto $6{p^6}$ both Radon and Plutonium have similar configuration. Hence, we can replace the electronic configuration of $86$ electrons by the symbol of Radon as $\left[ {Rn} \right]$.
So, the electronic configuration of plutonium will become $\left[ {Rn} \right]5{f^6}7{s^2}$.

Note:
We do not use Ununoctium as a reference noble gas because it has atomic number $118$ which is more than plutonium. Plutonium comes under the category of actinides. Plutonium is radioactive in nature and it is useful as a source of energy in nuclear weapons.