Nuclear radiation GapFill

Some isotopes are unstable. They can become more stable by undergoing radioactive decay, where they change their properties by emitting a particle or electromagnetic radiation.
The  count-rateactivityemissivitydose of a sample is the number of radioactive decays which occur per second, which has units of  sievertsroentgensbecquerelsteslas.
Nuclear decays can't be detected directly, but the radiation emitted during a nuclear decay can.  Geiger–Muller tubesThomson–Thompson chambersRutherford–Chadwick countersMarsden–Bragg detectors can count the number of radioactive emissions that pass through the detector itself, but cannot detect all of the decays produced by the sample.
The types of radioactive decay are:

•  AlphaNeutronGammaBeta decay, which releases a helium-4 nucleus, and reduces the mass number of the nucleus by 4 and the atomic number by 2.
•  GammaNeutronBetaAlpha decay, which releases a high-speed electron, and increases the atomic number of the nucleus by 1 but doesn't change the mass number.
•  BetaNeutronGammaAlpha decay, which releases high-energy electromagnetic radiation, and which doesn't affect the atomic or mass numbers of the nucleus.
•  NeutronBetaGammaAlpha decay, which releases a neutrally charged subatomic particle, and reduces the mass number of the nucleus by 1 but doesn't change the atomic number.

Nuclear decay is random, so it's impossible to predict when a particular nucleus will decay, but it is possible to use laws of probability to predict how many nuclei will decay in a given time period. The  count-ratedosehalf-lifeactivity of a sample is the time taken for the number of radioactive nuclei in the sample to reduce to half of its original value.
There are lots of hazards associated with nuclear decay.  EmissionContaminationIrradiationIonisation is when nuclear material gets onto or into another material.  IrradiationIonisationContaminationEmission is the exposure of a material to radiation.