The maximum number of electrons in a subshell of an atom is determined by which of the following expressions?

The correct set of four quantum numbers for the outermost electron of sodium $(Z=11)$ is

$A$ hydrogen atom has only one electron,so mutual repulsion between electrons is absent. However,in multielectron atoms,mutual repulsion between the electrons is significant. How does this affect the energy of an electron in the orbitals of the same principal quantum number in multielectron atoms?

In an element with atomic number $(Z) = 25$,the number of electrons with $(n+l)$ value equal to $3$ and $4$ are $x$ and $y$ respectively. The value of $(x+y)$ is

Which of the following orbitals will have zero probability of finding the electron in the $yz$ plane?

$A$ certain orbital has no angular nodes and two radial nodes. The orbital is