question_answer

Binding energy per nucleon relation with mass Number

A) first decreases then increases

B) first increases then decreases

C) increases                            

D) decreases

Correct Answer: B

Solution :

The variation of average binding energy per nucleon with mass number A is shown in figure. Mass number. (A) Average binding energy per nucleon for light nuclei like \[_{1}{{H}^{1}}{{,}_{1}}{{H}^{2}}{{,}_{1}}{{H}^{3}}\]is small. For mass numbers ranging from 2 to 20, there are sharply defined     peaks     corresponding     to \[_{2}H{{e}^{4}}{{,}_{6}}{{C}^{12}}{{,}_{8}}{{O}^{16}}\]etc. The binding energy curve has a broad maximum in the range A = 30 to 4 = 120 corresponding to average binding energy per nucleon = 8.5 MeV. The peak value of the maximum is 8.8 MeV/nucleon for \[_{26}F{{e}^{56}}\]. As the mass number increases, the binding energy per nucleon decreases gradually falling to about 7.6 MeV per nucleon for \[_{92}{{U}^{238}}\]