The maximum number of electrons that can be accommodated in the $M$ shell is

Figure $1$ shows the electron density distribution for a $2s$ orbital. Figure $2$ shows the radial wave function plot for a $2s$ orbital. Which of the following points $(A, B, C, D)$ in Figure $2$ most accurately represents the spherical nodal surface as shown in Figure $1$?

Which of the following electronic configurations has the least energy?

In a potassium atom,the electronic energy levels are in the following order:

The angular momentum of an electron depends on:

The electronic configuration of three elements $A$,$B$,and $C$ are given below. Stable form of $A$ may be represented by the formula:
$A : 1s^2, 2s^2, 2p^6$
$B : 1s^2, 2s^2, 2p^6, 3s^2, 3p^3$
$C : 1s^2, 2s^2, 2p^6, 3s^2, 3p^5$