§-Quick questions
NSWPhysicsModule 8: From the Universe to the Atom
Quick questions on Radioactive decay and half-life: HSC Physics Module 8
5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is alpha decay?Show answer
A heavy nucleus emits an alpha particle (He, two protons and two neutrons). The atomic number decreases by 2, mass number by 4.
What is beta-minus decay?Show answer
A neutron in the nucleus converts to a proton, emitting an electron (the beta particle) and an electron antineutrino. Atomic number increases by 1, mass number unchanged.
What is gamma decay?Show answer
The nucleus is left in an excited state after an alpha or beta decay (or after a nuclear reaction). It drops to a lower state by emitting a high-energy photon (gamma ray). No change in or .
What are balancing nuclear equations?Show answer
In any decay equation, two conservation laws must hold:
What is the decay law?Show answer
If is the number of undecayed nuclei at time , the rate of decay is proportional to :
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