For other definitions, see Q value

In nuclear physics and chemistry, the Q value for a reaction is the amount of energy released by that reaction: Q=E(\mbox{Reactants})-E(\mbox{Products})\!

A reaction with a positive Q value is exothermic, i.e., has a net release of energy, whilst a reaction with a negative Q value is endothermic, i.e., requires a net energy input.^[1]

Q values also feature in particle physics, for example in Sargent's rule, which states that the reaction rate of weak interactions is proportional to Q^5.

Notes and references

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