What do you mean by Q value of a nuclear reaction?

Explanation

Q-value of a nuclear reaction :
The energy absorbed or evolved during a nuclear reaction is known as Q-value of that nuclear reaction.
Q- value of that nuclear reaction will be positive if energy is evolved during the reaction. Q-value of that nuclear reaction will be negative if energy is absorbed during the reaction. The physical quantities which remain conserved during a nuclear reaction are:
(i) Mass number
(ii) Change number
(iii) Spin quantum number