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Radioactivity


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Rutherford's atomic model
proposed that atoms had a nucleus made up of protons and neutrons surrounded by orbits of electrons.
Isotopes
Atoms of the same element with different mass numbers.
Stable isotopes
protons and neutrons found in the nucleus are held together very strongly, they do not decay over time.
Unstable isotopes
atoms the neutrons and protons in the nucleus are not held together strongly, they decay over time.
Radioactive isotopes
another name for unstable isotopes, they decay over time into a more stable form.
Radioactive substances
emit nuclear radiation (because it comes from the nucleus).
Three types of nuclear radiation
Alpha particles, beta particles and gamma rays.
Alpha particles
helium nucleus (2 protons and 2 neutrons)
Beta particles
same size as an electron, but can carry a positive or negative charge
Gamma radiation
are not particles but bursts of energy (associated with the release of alpha and beta particles)
Half life
The time taken for half of all the nuclei in a sample of a radioisotope to disintegrate or decay to a stable form.
Smoke alarms
use radiation to build a circuit, which is disrupted by smoke, causing the alarm to sound.
Cosmic radiation
is radiation from space
Background radiation
is naturally emitted from elements in the Earth's crust