Question:
Consider the hypothetical situation where the azimuthal quantum number, $l$, takes values $0,1,2, \ldots . . n+1$, where $n$ is the principal quantum number. Then, the element with atomic number:
Correct Option: , 2
Solution:
Under the given situation for
$n=1, l=0,1,2$
$n=2, l=0,1,2,3$
$n=3, l=0,1,2,3,4$
According to $(n+l)$ rule of order of filling of subshells will be :
$1 s 1 p 1 d 2 s 2 p 3 s 2 d 3 f$
Atomic number 6 $1 s^{2} 1 p^{4}$
Atomic number 9$1 s^{2} 1 p^{6} 1 d^{1}$
Atomic number 8 $1 s^{2} 1 p^{6}$
Atomic number 13 $1 s^{2} 1 p^{6} 1 d^{5}$
Therefore option (b) is correct. Atomic number of first noble gas will be $18\left(1 s^{2} 1 p^{6} 1 d^{10}\right)$.