Question

The above is a plot of binding energy per nucleon E_b, against the nuclear mass M; A, B, C, D, E, F correspond to different nuclei. Consider four reactions:

(i) A + B → C + ε (ii) C → A + B + ε
(iii) D + E → F + ε (iv) F → D + E + ε
where ε is the energy released? In which reactions is ε positive?
(a) (i) and (iv) 

(b) (i) and (iii)

(c) (ii) and (iv) 

(d) (ii) and (iii)

Answer 1

(a) :- When two nucleons combine to form a third one, and energy is released, one has fusion reaction. If a single nucleus splits into two, one has fission. The possibility of fusion is more for light elements and fission takes place for heavy elements. 

Out of the choices given for fusion, only A and B are light elements and D and E are heavy elements. Therefore A + B → C + ε is correct. In the possibility of fission is only for F and not C. Therefore F → D + E + ε is the correct choice.