In every nuclear reaction
Nuclear & Particle Physics - OCR A-Level Physics
- In every nuclear reaction, the following are conserved:
- ChargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). (total atomic number Z $before = total after)$.
- Nucleon numberThe total number of protons and neutrons in a nucleus (also called mass number, A). (total mass number A $before = total after)$.
- Lepton numberA quantum number conserved in all interactions. Leptons (electrons, neutrinos) have lepton numberA quantum number conserved in all interactions. Leptons (electrons, neutrinos) have lepton number +1, antileptons have -1, and hadrons have 0. +1, antileptons have -1, and hadrons have 0. (electrons and neutrinos are leptons with $L = +1$; their antiparticles have $L = -1)$.
- Baryon numberA quantum number conserved in all interactions. Baryons (protons, neutrons) have baryon numberA quantum number conserved in all interactions. Baryons (protons, neutrons) have baryon number +1, antibaryons have -1, and mesons/leptons have 0. +1, antibaryons have -1, and mesons/leptons have 0. (protons and neutrons are baryons with B = +1; antibaryons have $B = -1)$.
- EnergyThe capacity to do work. Measured in joules (J). and momentumThe product of an object's mass and velocity: p = mv. A vector quantity measured in kg m s⁻¹. are also conserved (including mass-energyThe capacity to do work. Measured in joules (J). equivalence).
Examiner Tips and Tricks
- When asked to check whether a reaction is possible, verify conservation of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). (Z), nucleon number (A), lepton numberA quantum number conserved in all interactions. Leptons (electrons, neutrinos) have lepton number +1, antileptons have -1, and hadrons have 0. (L), and baryon numberA quantum number conserved in all interactions. Baryons (protons, neutrons) have baryon number +1, antibaryons have -1, and mesons/leptons have 0. (B).
- If any one is not conserved, the reaction cannot occur.