Compare to some nearby odd-numbered elements: Rubidium (37), yttrium (39), niobium (41), and rhodium (45) all have only one stable isotope. The concept of a magic number may also help in understanding this. Last edited by BorgHunter; 02-08-2009 at 05:24 PM . Reason: Corrected spelling of "nucleon" BorgHunter View Public Profile Find