How many electrons can be fit into the orbitals that comprise the $3^{rd}$ quantum shell $(n = 3)$?

Total number of unpaired electrons in an atom of atomic number $29$ is

What is the total number of unpaired electrons present in the observed electronic configuration of $Cr$ $(Z=24)$?

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:

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

Which rule describes the arrangement of electrons in subshells of the same energy?