Nuclear Chemistry and Isotopes in Applications
The nucleus as a chemical exception
Types of decay
Nuclear chemistry focuses on changes in the nucleus rather than the electron cloud. Common decay modes include alpha decay, beta decay, and gamma emission, each changing the nucleus in characteristic ways.
Decay overview
| Decay type | Particle emitted | Typical effect |
|---|---|---|
| Alpha | nucleus | Mass number decreases by and atomic number decreases by |
| Beta minus | Electron | Neutron converts to proton |
| Beta plus | Positron | Proton converts to neutron |
| Gamma | Photon | Nucleus loses energy without changing or |
Half-life
Radioactive decay follows first-order kinetics in nuclear contexts, with half-life describing the time required for half of a sample to decay. After half-lives, the remaining amount is
Practical use
Radioisotopes are used in medical imaging, cancer treatment, tracers, smoke detectors, and dating archaeological samples.
After two half-lives, what fraction of a radioactive sample remains?
Each half-life halves the sample; after two half-lives, remains.
Correct answer:
What changes in the nucleus during alpha decay?
An alpha particle is a helium nucleus, so emission removes 2 protons and 2 neutrons.
Correct answer: The mass number decreases by 4 and atomic number decreases by 2
Stable vs unstable nuclei
Stable nuclei
- Balanced neutron-to-proton ratio
- Do not spontaneously decay
Unstable nuclei
- Excess nuclear energy or imbalance
- Undergo radioactive decay
A positron is best described as
A positron has the same mass as an electron but opposite charge.
Correct answer: The electron's antiparticle