Q-Value
The net amount of energy released or absorbed during a nuclear reaction or radioactive decay process.
Governing formula
Q = (m_reactants - m_products) c²
SI unit
MeV (Mega-electronvolts)
In depth
If Q > 0, the reaction is exothermic (exoergic), converting rest mass defect into kinetic energy and photon radiation. If Q < 0, the reaction is endothermic (endoergic), requiring threshold kinetic energy input to proceed.
Examples in the real world
Determining the Q-value = 17.6 MeV released in the Deuterium-Tritium (D-T) nuclear fusion reaction.