<P> The quantum number m (\ displaystyle m) refers, loosely, to the direction of the angular momentum vector . The magnetic quantum number m (\ displaystyle m) only affects the electron's energy if it is in a magnetic field because in the absence of one, all spherical harmonics corresponding to the different arbitrary values of m (\ displaystyle m) are equivalent . The magnetic quantum number determines the energy shift of an atomic orbital due to an external magnetic field (the Zeeman effect)--hence the name magnetic quantum number . However, the actual magnetic dipole moment of an electron in an atomic orbital arrives not only from the electron angular momentum, but also from the electron spin, expressed in the spin quantum number . </P> <P> Since each electron has a magnetic moment in a magnetic field, it will be subject to a torque which tends to make the vector L (\ displaystyle \ mathbf (L)) parallel to the field, a phenomenon known as Larmor precession . </P>

Determine the value of the quantum number n if the maximum allowed value for l is 0