Which of the following rules is violated by the given electronic configuration?

The number of electrons in a nickel $(Ni)$ atom having $m = 0$ is:

The wave function $(\Psi)$ of $2s$ is given by
$\Psi_{2s} = \frac{1}{2\sqrt{2\pi}} \left(\frac{1}{a_0}\right)^{3/2} \left(2 - \frac{r}{a_0}\right) e^{-r/2a_0}$
At $r = r_0$,a radial node is formed. Thus,$r_0$ in terms of $a_0$ is:

Number of electrons that Vanadium $(Z=23)$ has in p-orbitals is equal to $......$

Which of the following sets of quantum numbers is not possible?

$Be$'s $4^{th}$ electron will have four quantum numbers $(n, l, m, s)$: