What is the principal quantum number for the second period?

Hint: We have to know that the quantum is described as the set of numbers which is used to determine the position and energy of an electron present in the atom. There are a total of four quantum numbers. Principal quantum number, which is denoted as n, orbital angular quantum number (l), magnetic quantum number (\[{m_I}\]) and electron spin quantum number \[\left( {{m_s}} \right)\].

Complete answer:
As we know, the principal quantum number for the second period is equal to two. The principal quantum number deputes the principal electron shell present in the atom. Hence, it determines the feasible distance present between the electrons and the nucleus. The principal quantum number is directly proportional to the distance between the nucleus and the electrons or directly proportional to the atomic size. The value of n may be any of the integers which should be greater than one. And it indicates the innermost electron present in an atom.
In the second period, the principal quantum number is equal to two. Because it contains the outer electronic configuration, \[2s\] and \[2p\]. Which means, the value of n is equal to two.

Note:
We need to remember that the principal quantum number determines the distance between the electrons and nucleus and it is directly proportional to the atomic size. The possible values of the principal quantum number may be \[1,2,3,4,...\]. Azimuthal quantum number also known as orbital angular momentum quantum numbers and the possible values of l is \[0,1,2,3,4,..,\left( {n - 1} \right)\]. The value of magnetic quantum \[{m_I}\]is equal to \[ - l,..., - 1,0,1...,l\]. And the possible values of electron spin quantum number \[\left( {{m_s}} \right)\] is \[ + \dfrac{1}{2}, - \dfrac{1}{2}\].