The strong neutron excess (defined as N - Z) of high-mass nuclei is illustrated by noting that most high-mass nuclides could never fission into two stable nuclei without neutrons being left over. For example, consider the spontaneous fission of a 235U nucleus into two stable daughter nuclei with atomic numbers 39 and 53. From Appendix F, determine the name of the

(a) First and

(b) Second daughter nucleus. From Figure, approximately how many neutrons are in the (c) First and

(d) Second?

(e) Approximately how many neutrons are left over?

100 60 40 20 60 80 Neutron number N 120 20 40 100 140 160 Proton number /