The rate at which an unstable nucleus decays. The activity of a radioactive source reduces over time.
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Alpha Particle
A positively charged particle consisting of two protons and two neutrons.
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Atomic Number
The number of protons found in an atom of a specific element. Each element has a different atomic number.
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Background Radiation
Radiation that is found in small quantities all around us and originates from natural sources such as rocks and cosmic rays, as well as from man-made sources such as nuclear weapons testing and accidents.
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Becquerel
The unit of radioactive activity.
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Beta Particle
A high speed electron that a nucleus emits when a neutron converts into a proton.
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Bohr Model
A model of the atom that suggested that electrons orbit the nucleus at set distances.
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Chain Reaction
The process of neutrons released by a fission reaction, being absorbed by another unstable, large nuclei, and inducing further fission.
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Electrons
A negatively charged constituent of the atom, that are found in different energy levels, around the nucleus.
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Element
A substance that cannot be chemically broken down into other substances. Each element has a characteristic number of protons in its nucleus.
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Energy Levels
The stable states in which electrons are found in around a nucleus. Electrons can transition to a higher energy level through the absorption of electromagnetic radiation and can transition to a lower energy level through the emission of electromagnetic ra
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Fission Products
Fission products two smaller nuclei, two or three neutrons and gamma rays. All these products are released with kinetic energy.
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Gamma Ray
Electromagnetic radiation emitted from a nucleus.
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Geiger-Muller Tube
A device used to detect ionising radiation.
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Half-Life
The time it takes for the number of unstable nuclei of an isotope in a sample to halve, or the time it takes for the initial count rate of a sample of the isotope to halve.
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Ions
Atoms with a resultant charge due to the loss or gain of electrons.
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Irradiation
The process of an object being exposed to nuclear radiation. The object does not become radioactive.
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Isotopes
Atoms with the same number of protons but different numbers of neutrons. The atomic number is the same, but the mass number is different.
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Mass Number
The number of protons and neutrons in an atom.
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Negative Ions
Atoms that gained electrons and so have a resultant negative charge.
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Neutrons
A neutrally charged constituent of the nucleus.
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Nuclear Fission
The splitting of a large and unstable nucleus into two smaller and more stable nuclei to produce energy. This is the method currently used in nuclear power stations.
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Nuclear Fusion
The joining of two small, light nuclei to form a larger, heavier one and release energy. It cannot happen at low pressures and temperatures since in these conditions the electrostatic repulsion of protons in the nucleus cannot be overcome.
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Nucleus
The positively charged centre of the atom, containing protons and neutrons.
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PET Scanner
A medical imaging device that uses radioactive tracers and detectors to form internal body images.
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Plum Pudding Model
An old model of the atom that represented the atom as a ball of positive charge, with negative charges distributed throughout it.
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Positive Ions
Atoms that have lost electrons and so have a resultant positive charge.
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Protons
A positively charged constituent of the nucleus.
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Radioactive Contamination
The unwanted presence of radioactive atoms on other materials. It is hazardous due to the decay of the contaminating atoms.
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Radioactive Decay
The random process involving unstable nuclei emitting radiation to become more stable.
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Random Nature of Radioactive Decay
You cannot predict which nuclei in a radioactive sample will decay next, or when the next decay will occur - it is a random process.
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Other cards in this set
Card 2
Front
Alpha Particle
Back
A positively charged particle consisting of two protons and two neutrons.
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