Question

Which block of the periodic table contains elements with general electronic configuration?
$(n - 2){f^{1 - 14}}(n - 1){d^{0 - 1}}n{s^{1 - 2}}$
A) s-block
B) p-block
C) d-block
D) f-block

Answer 1

Hint: Differentiating electron entered into antipenultimate shell. The elements of this block are placed at the bottom of the periodic table. Most of the elements of this block are radioactive.

Complete step by step solution:
This is the general electronic configuration $(n - 2){f^{1 - 14}}(n - 1){d^{0 - 1}}n{s^{1 - 2}}$
As per Aufbau principle the lowest energy orbital fills first. As per the given configuration,
this is the decreasing order of energy of orbitals
\[s < p < d < f\]
So first s-orbital gets filled up second p –orbital gets filled up third d-orbital gets filled up fourth f-orbital gets filled up.
In the configuration we can differentiate
1 .Ultimate shell is valency shell , it is \[n{s^{1 - 2}}\]
2 .Penultimate shell is present before the valence shell in atom , it is \[(n - 1){d^{0 - 1}}\]
3. Antipenultimate shell is present before the penultimate shell , it is \[(n - 2){f^{1 - 14}}\]
S-block : The differentiating electron enters in the s- subshell called as s-block elements.
P-block : The differentiating electron enters into a p-subshell called p-block elements.
d-block :The differentiating electron enters into a d-subshell called as d-block elements.
f-block : The differentiating electron enters into an f-subshell called as f-block elements.
Differentiating electron is the last electron that is added to the last to the valence shell
So as per the given electronic configuration differentiating electron enters into f-subshell , so it belongs to f-block.
f-block elements are inner transition elements or rare earth elements. Examples for the inner transition elements are Thorium, Proctainium , Uranium ,Neptunium Plutonium , Americium ,Curium and Berkelium.
The electronic configuration of Uranium is \[(Rn)5{f^3}6{d^1}7{s^2}\].
These f-block elements are arranged at the bottom of the periodic table and these f-block elements placed In 3rd and 4 th group.
These f-block elements differentiated into Lanthanides and Actinides.
Hence, answer is (d) f-block

Note: f-block elements start from the fourth period and d-block elements also placed started from 3rd period but d-block elements are placed between s and p-block elements.