According to the Aufbau principle,which of the three $4d$,$5p$,and $5s$ will be filled with electrons first?

Which of the following species has an equal number of electrons in the outermost shell and the penultimate shell?

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.

How are atomic orbitals (electrons) identified or distinguished?

Total number of angular nodes of orbitals associated with third shell $(n=3)$ of an atom is

For which of the following sets of quantum numbers,an electron will have the highest energy?