Question

Shivam, a student of class XIth had difficulty to understand rules for writing the electronic configuration of the elements. Shivam is a very shy boy and hesitate to ask questions in class. Shravan one of his classmates discussed this problem with his teacher. The teacher called Shivam to staffroom and explained the concept in detail. Shivam, then got satisfied.
(i) What rules were told to Shivam by his teacher?
(ii) Write the electronic configuration of Cu.
(iii) What values are displayed by Shravan.

Answer 1

"Rules for filling electrons in orbitals - Aufbau principle

"Electrons" are added "one at a time" to the "lowest energy orbitals" available until all the "electrons" of the "atom" which have been taken into account.

According to the "Aufbau principle", electrons fill lower energy orbitals first.

Pauli's exclusion principle and Hund's rule

Pauli's exclusion principle:

"No two electrons" in an orbital can have same value for all "four quantum numbers"."

"Hund's rule":

"Pairing of electrons" in an orbital should not take place until all orbitals are "singly occupied".

ii) Electronic configuration of Copper:

Copper electronic configuration -$[Ar]\quad { 3d }^{ 10 }{ 4s }^{ 1 }$

iii) $[Ar]\quad { 3d }^{ 10 }{ 4s }^{ 1 }"$