Question

How many elements are possible for 1st period of periodic table if azimuthal quantum number can have integral values from $0,1,2(n+1)$?

Answer 1

According to question value of azimuthal quantum number is 0 to (n+1)

Therefore, for n = 1, l = 0, 1, 2

for n = 2 , l = 0, 1, 2, 3

Now applying $(n+l)$ rule we get subshell

filling order like this :

$1s,1p,2s,...$

After $1p$, the second shell starts filling only the elements having electrons present in $1s$ and $1p$ will belong to $1st$ period.

Total Number of such element possible is

$2\times$ (capacity of 1s subshell)+6 (capacity of$1p$ subshell)

which is equal to '8' elements.