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

The number of $d-$ electrons in $Fe^{2+} \ (Z = 26)$ is not equal to the number of electrons in which one of the following?

The following sets of quantum numbers represent four electrons in an atom:
$(i)$ $n = 4, l = 1$ $(ii)$ $n = 4, l = 0$
$(iii)$ $n = 3, l = 2$ $(iv)$ $n = 3, l = 1$
The sequence representing the increasing order of energy is:

What is the maximum number of electrons that can be associated with the following set of quantum numbers?
$n = 3, l = 1$ and $m = -1$

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.

Maximum number of electrons that can be accommodated in the subshell with azimuthal quantum number $l=4$ is