The atomic symbol superscript 206 subscript 82 upper p b. represents lead-206 (pb-206), an isotope that has 82 protons and 124 neutrons. which atomic symbol could represent an isotope that undergoes radioactive decay to produce pb-206? superscript 238 subscript 92 upper u. superscript 222 subscript 87 upper p b superscript 178 subscript 72 upper h f. superscript 192 subscript 77 upper p b.