The total number of orbitals in an energy level designated by principal quantum number $n$ is equal to

Identify the correct statements among the following:
$i. E_{2s}(H) > E_{2s}(Li) < E_{2s}(Na) > E_{2s}(K)$
$ii.$ The maximum number of electrons in the shell with principal quantum number $n$ is equal to $2n^2$.
$iii.$ Extra stability of half-filled subshell is due to smaller exchange energy.
$iv.$ Only two electrons,irrespective of their spin,may exist in the same orbital.

Which of the following statements are true?
$(A)$ The subsidiary quantum number $\ell$ describes the shape of the orbital occupied by the electron.
$(B)$ The image shows the boundary surface diagram of the $2p_x$ orbital.
$(C)$ The $+$ and $-$ signs in the wave function of the $2p_x$ orbital refer to charge.
$(D)$ The wave function of the $2p_x$ orbital is zero everywhere in the $yz$ plane.

The two electrons have the following set of quantum numbers:
$P = 3, 2, -2, +1/2$
$Q = 3, 0, 0, +1/2$
Which of the following statements is true?

$4s^2$ is the configuration of the outermost orbit of an element. Its atomic number would be $:-$

Which of the following represents the correct set of four quantum numbers for a $4d$ electron?