If the value of $(n+\ell)$ is not greater than $3$,which of the following subshells is not possible $-$

The atomic weight of an element is twice its atomic number. If the $2p$ subshell contains three electrons,the element is .......

Which orbital is closer to the nucleus: $2p$ or $3p$?

The difference between the orbital angular momentum of an electron in a $4f$ orbital and another electron in a $4s$ orbital is

The quantum numbers of four electrons are given below:
$I. \ n = 4, l = 2, m_l = -2, m_s = -1/2$
$II. \ n = 3, l = 2, m_l = 1, m_s = +1/2$
$III. \ n = 4, l = 1, m_l = 0, m_s = +1/2$
$IV. \ n = 3, l = 1, m_l = 1, m_s = -1/2$
The correct order of their increasing energies will be:

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.