The set of quantum numbers for the $19^{th}$ electron in chromium $(Cr)$ is:

Which of the following statements are correct?
$(a)$ When an electron in an atom moves from $n=4$ to $n=2$,it gains energy.
$(b)$ An electron in a $3p$ orbital would have less energy than an electron in a $2p$ orbital.
$(c)$ $A$ $3s$ subshell has a maximum of $2$ electrons.
$(d)$ $A$ $3^{rd}$ orbit may contain a maximum of $10$ electrons.

The maximum number of electrons in an atom with $l = 2$ and $n = 3$ is

The quantum numbers $+1/2$ and $-1/2$ for the electron spin represent

The orbital angular momentum of an electron in $2s$ orbitals is

The five valence electrons of $P^{15}$ are labeled as $A, B, X, Y, Z$ as shown in the figure. If the spin quantum number of $B$ and $Z$ is $+\frac{1}{2}$,identify the group of electrons that share three identical quantum numbers.