Question

In which of the following periods, a maximum number of 32 elements are present?
This question has multiple correct options
A.4th
B.6th
C.3rd
D.7th

Answer 1

We have to know that electrons are filled in increasing order of energy levels i.e. the electrons occupy the orbitals of lower energy and then, occupy the orbitals of higher energy.

Complete step by step answer: We know that the order of filling electrons is,
${\text{ }}1s{\text{ }}2s{\text{ }}2p{\text{ }}3s{\text{ }}3p{\text{ }}4s{\text{ }}3d{\text{ }}4p{\text{ }}5s{\text{ }}4d{\text{ }}5p{\text{ }}6s{\text{ }}4f{\text{ }}5d{\text{ }}6p{\text{ }}7s{\text{ }}5f{\text{ }}6d{\text{ }}7p{\text{ }}6f{\text{ }}7d{\text{ }}7f{\text{ }}.{\text{ }}.{\text{ }}.{\text{ }}.{\text{ }}.$
The maximum number of electrons held by s orbital is two.
The maximum number of electrons held by p orbital is six.
The maximum number of electrons held by d orbital is ten.
The maximum number of electrons held by f orbital is fourteen.
Now let us see the number of elements present in each period.
4th period: We know that period four begins with 4s orbital. Once, the electron occupies the 4s orbitals, it jumps to the 3d orbital, and then goes to 4p orbitals. So, the total number of electrons is $2 + 10 + 6 = 18$. We have calculated that 18 elements are in the 4th period. Therefore, the option (A) is incorrect.
6th period: We know that period six begins with 6s orbital. Between the orbitals of 6s and 6p, the electrons jump to the 4f and 5d orbitals. So, the total number of electrons are $2 + 14 + 10 + 6 = 32$. So, the number of elements in the 6th period is 32 elements.
Therefore, the Option (B) is correct.
3rd period: We know that period three begins with 3s orbital. Once the electron occupies the 3s orbitals, it jumps to the 3p orbital. So, the total number of electrons is $2 + 6 = 8$. We have calculated that 8 elements are in the 3rd period.
Therefore, the option (C) is incorrect.
7th period: We know that period seven begins with 7s orbital. Between the orbitals of 7s and 7p, the electrons jump to the 5f and 6d orbitals. So, the total number of electrons are $2 + 14 + 10 + 6 = 32$. So, the number of elements in the 7th period is 32 elements.
Therefore, the option (D) is correct.
In 6th and 7th periods, a maximum number of 32 elements are present.
Therefore, the options (B) and (D) are correct.

Note: We must remember that the longest periods in the periodic tables are 6th and 7th periods. Noble gases end every period. In the 1st period two elements are present. In the 2nd period, eight elements are present. In the 5th period, 18 elements are present.