BRAINCAKERadioactivity
Revision notes for Radioactivity in OCR Physics A (J249). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.
- Protons and neutrons in the nucleusAt the centre of every atom is a tiny nucleus.
- Isotopes and nuclear massAll atoms of one element have the same number of protons, but they do not all have the same number of neutrons.
- Nuclear symbols and isotopesA nucleus is written as a symbol with two numbers.
- Unstable nuclei and types of radiationSome nuclei are unstable.
- How emissions change the nucleusWhen an unstable nucleus emits radiation, its mass number, its atomic number, or both can change.
- Writing nuclear decay equationsA nuclear equation shows the nucleus before decay on the left and the new nucleus and the emitted particle on the right.
- Balancing nuclear equationsA nuclear equation shows an unstable nucleus decaying.
- Electron energy levels and ionisationThe electrons in an atom are arranged at different distances from the nucleus.
- Radiation from atoms and nucleiChanges in atoms and in nuclei can generate and absorb radiation.
- Half-life and random decayRadioactive decay is random.
- Net decline over a number of half-livesEach half-life halves the activity again.
- Penetrating power of alpha, beta and gammaThe three types of radiation differ in how far they can pass through materials.
- Contamination and irradiationRadioactive material can harm people in two different ways.
- Half-life and the hazard of radioactive materialThe half-life of a radioactive material is the time it takes for its activity to fall to half of its starting value.
- Medical uses of radiationNuclear radiation has important uses in medicine.
- Nuclear fissionSome large nuclei, such as uranium-235 and plutonium-239, are unstable.
- Nuclear fusionIn nuclear fusion two light nuclei join together to form one heavier nucleus.