The sum of electrons present in all subshells of an atom with $m_s$ value of $+\frac{1}{2}$ for $n=4$ and $m_s$ value of $-\frac{1}{2}$ for $n=3$ is

Statement $A$: In a potassium atom,the $19^{th}$ electron enters the $4s$-orbital instead of the $3d$-orbital.
Reason $R$: The $(n + l)$ rule is followed to determine the minimum energy of an orbital.

Which quantum number determines the shape of the subshell?

The quantum number which may be designated by $s$,$p$,$d$ and $f$ instead of numbers is

The electronic configuration of chromium ($Cr$,$Z=24$) is:

What is the maximum number of orbitals that can be identified with the following quantum numbers?
$n = 3, l = 1, m_l = 0$