Question

Packing fraction of elements A, B, C are $-20,-27,+18,$ respectively. Arrange them in the increasing order of stability.

• A. C < A < B
• B. A < B < C
• C. A < C < B
• D. None of them

Answer 1

The correct option is A C < A < B

The difference of actual isotopic mass and the mass number in terms of packing fraction is defined.

The value of packing fraction depends upon the manner of packing of the nucleons within the nucleus. Its value can be negative, positive or even zero. A negative packing fraction generally indicates stability of the nucleus.

In general, lower the packing fraction, greater is the binding energy per nucleon and hence, greater is the stability. The relatively low packing fraction of He, C and O imply their exceptional stability, packing fraction is least for Fe (negative) and highest for H (+78).

So, the order is $C<A<B$.