# Inner electrons 157 # Outer electrons 100 # Protons 257 An-Isotope 100:257 Approval Stats BE - Actual 1907.50 BE - Nucleon 7422.19 Decay A 99.79, SF 0.21 Element Fermium Half Life 100.5 d Mass Actual 257.10 Mass Calculated 259.01 Mass H Norm 255.10 Stability Unstable
