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P4 (Models of the atom, Radioactive decay, Atoms, isotopes, ions, Uses and…
P4
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Radioactive decay
stable nuclei
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atoms near the start with a fewer amount of protons are stable when they have an equal amount of neutrons
as the number of protons increases, more and more neutrons are needed to make it stable
Nuclear radiation
an unstable nucleus can decay by emitting an alpha particle, beta particle or gamma ray ... or a single neutron
alpha
If the nucleus has too few neutrons, it will emit a ‘package’ of two protons and two neutrons called an alpha particle.
beta
If the nucleus has too many neutrons, a neutron will turn into a proton and emit a fast-moving electron (beta particle)
gamma
After emitting an alpha or beta particle, the nucleus will often still be too ‘hot’ and will lose energy in a similar way to how a hot gas cools down. A hot gas cools by emitting
infrared radiation
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half life
not all nuclei are likely to decay at the same time so it is impossible to tell when a particular nucleus will decay.
It is not possible to say which particular nucleus will decay next, but given that there are so many of them, it is possible to say that a certain number will decay in a certain time.
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Half-life is the time it takes for half of the unstable nuclei in a sample to decay or for the activity of the sample to halve or for the count rate to halve. Count-rate is the number of decays recorded each second by a detector, such as the Geiger-Muller tube.
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