Question

State whether the following statement is true or false:
The 6th period is the longest period in the modern periodic table.

Answer 1

When the last s-orbital in the electronic configuration of an element is $ns$, then the element belongs to the nth period. Which means the electrons of the element occupies the nth s-orbital, nth p-orbital, (n-1)th d-orbital and (n-2)th f-orbital. S-orbital can accommodate at most 2 electrons, p-orbital can accommodate at most 6 electrons, d-orbital can accommodate at most 10 electrons and f-orbital can accommodate at most 14 electrons. Use this information to state whether the given statement is true or false.

Complete step by step solution:
Modern periodic table contains 18 groups, 7 periods and 118 elements.
The elements in the first period have an electronic configuration ranging from $1{s^1}$ to $1{s^2}$. This period has only two elements as s-orbital can accommodate only two elements.
Elements in the second period have both s-block and p-block elements. Total elements present in the 2nd period are 8 elements $1{s^2}2{s^1}$ to $1{s^2}2{s^2}2{p^6}$.
In the same way 3rd period also have 8 elements $1{s^2}2{s^2}2{p^6}3{s^1}$ to $1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}$.
4th and 5th period have 18 elements ($1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^1}$ to $1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^{10}}4{p^6}$;$1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^{10}}4{p^6}5{s^1}$ to $1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^{10}}4{p^6}5{s^2}4{d^{10}}5{p^6}$) each including d-block elements, nth p-orbital has (n-1)th d-orbital.
The 6th period has 32 elements as the nth p-orbital has a (n-1)th d-orbital and (n-2)th f-orbital. F-block accommodates 14 elements, $1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^{10}}4{p^6}5{s^2}4{d^{10}}5{p^6}6{s^1}$ to $1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^{10}}4{p^6}5{s^2}4{d^{10}}5{p^6}6{s^2}4{f^{14}}5{d^{10}}6{p^6}$
The 7th period is an incomplete period as the elements cannot be given permanent recognition.
Therefore, the longest period of the periodic table is the 6th period having 32 elements.

**Therefore, the given statement is true.

Note: **
In the 7th period, the elements with atomic numbers 113, 115, 117 and 118 are unknown before. But two of these four elements have been verified and will get their permanents soon. But the other two elements are still not verified as their lifetime is one thousandth of a second. As the elements are unknown this period is considered to be incomplete else 6th and 7th will be the longest periods of the modern periodic table containing 32 elements each.