[allah_akbr]

is not the orbital an imaginary thing?
if so why there is an empty orbital although the motion of the electron is the one which specifies an orbital?

[movies]

Orbitals are imaginary, but they do represent the probability of where the electrons are at.  So, an empty orbital is where the electrons aren't at.  Different orbitals also represent different energy levels, so the electron probability for a certain energy level is what really makes up an orbital.  In that sense, an empty orbital indicates where the electrons would be at if they were there.

[allah_akbr]

thanx