Chemical Shift
Up to this point, we have been treating nuclei in general terms.
Simply comparing 1H, 13C, 15N etc.
If all 1H resonate at 500MHz at a field strength of 11.7T,
NMR would not be very interesting
Beff = Bo - Bloc  ---   Beff = Bo( 1 - s )
s is the magnetic shielding of the nucleus
The chemical environment for each nuclei results in a unique local magnetic field (Bloc) for each nuclei: