The atomic number of the element having the maximum number of unpaired electrons (in the ground state) is ........

Correct statements for an element with atomic number $9$ are:
$A.$ There can be $5$ electrons for which $m_{s}=+\frac{1}{2}$ and $4$ electrons for which $m_{s}=-\frac{1}{2}$
$B.$ There is only one electron in $p_z$ orbital
$C.$ The last electron goes to an orbital with $n=2$ and $l=1$
$D.$ The sum of angular nodes of all the atomic orbitals is $1$
Choose the correct answer from the options given below:

Which orbital is represented by the wave function $\Psi_{310}$?

$2p$ orbitals have

Which electron is associated with the least energy?

Which of the following statement$(s)$ is/are true?
$A$. If two orbitals have the same value of $(n+l)$, the orbital with lower value of $n$ will have lower energy.
$B$. Energies of the orbitals in the same subshell increase with increase in atomic number.
$C$. The size of $2p_x$ orbital is less than the size of $3p_x$ orbital.
$D$. Among $5f, 6s, 4d, 5p$ and $5d$ orbitals, none of the orbitals have $2$ radial nodes.