Shielding and Deshielding of Nuclei
•The magnetic field at the nucleus, B, (the effective field) is therefore generally less than the applied field, Bo, by a fraction . 
•                      B = Bo (1-s)
•peaks move to right due to shileding
•peaks move to left due to deshileding: beeing attached more electronegitve atoms or experiencing ring currents as in benezne