How the number of electron is …

Because the n.c.e.r.t has not given the line of quantum number but thank you for the link

https://youtu.be/TIxiDESxc0I ☝️☝️☝️☝️☝️Chemistry 3.1 Introduction to the Periodic Table – YouTube ...................,........................... https://courses.lumenlearning.com/boundless-chemistry/chapter/the-periodic-table/

Can you don't tell according to n.c.e.r.t lines which can be easier for understanding

ANSWER=................. Prediction of Period ⟶ In the electronic configuration of an atom, the principal quantum number (n) of the valence electrons represents the period of an element..... .. .. . ... ... ... Prediction of Block ⟶ The orbital out of s,p,d and f which receives the last electron represents the block of an element.............................. ....................... Prediction of Group ⟶ The group prediction occurs with the help of block as:- ............................................... (1) For s block: Group Number = Number of valence e− ......................... (2) For d block: Group Number = Number of e− in (n−1)d subshell + number ............................ of e− in ns subshell ..... ... . (3) For p block: Group Number = Number of valence e−+10 ...... B..... (4) For f-block: Group Number = 3 (always) ........ For example for chlorine with Z=17 ....... ... Electronic configuration = 1s22s22p63s23p5 .. .... Since the last e− enters in p - subshell: ...... ... (i) ∴ Block will be ′p′ . ...... (ii) For group we have element in p-block ... .. ∴ Group number = 10+ Valence e− in s subshell + Valence e− in p subshell . ... . . . Group Number = 10+2+5=17 . . (iii) For period . . The quantum number of valence e−=3 .. . ∴ Period number = 3