The principal quantum number of an atom represents:

Correct set of four quantum numbers for the outermost electron of rubidium $(Z=37)$ is :

The electronic configuration of $Cu$ is

Assertion $(A)$: Atoms with completely filled and half-filled subshells are stable.
Reason $(R)$: Completely filled and half-filled subshells have symmetrical distribution of electrons and have maximum exchange energy.
The correct answer is:

Which orbital is dumb-bell shaped?

For a $d$ electron,the orbital angular momentum is