To describe the state of an electron in an atom, we need quantum numbers.
- principal Q no.
- -
- goes from 1
to higher integer values.
- azimuthal Q no.
- -
- goes from 0
to
in integral steps - related to the magnitude of the angular
momentum.

- - goes from
to
. It
gives information about the component of angular momentum along any
particular direction, which you call
. It is not possible in quantum
mechanics to get all three components of momentum with certainty.
The best you can do is to get the magnitude and one component.
- spin Q no.
- -
for the electron which
is always
. This is needed to reconcile the requirement
of angular coservation when quatum mechanics is extended to the relativistic
realm. It is the magnitude of the intrinsic angular momentum of the
electron.

- - just like
, but for the electronic spin.
Pauli's exclusion principle (1925) states that no
two Fermions (electrons in this case) can have the same set of these
numbers if they share the same position in space (i.e. if they are
sufficiently close together).
Stirling Engine
2020-01-02