phosphorus atom phosphorus-33 atom (33)15P (33)P 0 30.974 32.97173 CAS:15749-66-3 CHEBI:37973 InChI=1S/P/i1+2 OAICVXFJPJFONN-NJFSPNSNSA-N P The radioactive isotope of phosphorus with relative atomic mass 32.971725, half-life of 25.34 days and nuclear spin (1)/2. [33P] chebi.owl chebi_ontology obi.owl phosphorus, isotope of mass 33 phosphorus-33 phosphorus-33