How does the orbital energy change as the nuclear charge increases from $Ne$ to $Ca$?

Arrange the following orbitals in increasing order of energy based on the given values of principal quantum number $(n)$ and azimuthal quantum number $(l)$:
$(1) n = 4, l = 1$
$(2) n = 4, l = 0$
$(3) n = 3, l = 1$
$(4) n = 3, l = 2$

According to the Aufbau principle,which orbital is filled with electrons immediately after the $5f$ orbital?

Which of the following outer electronic configurations represents argon?

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

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: