the unit of activity
positively charged sub-atomic particle found in the nucleus
a subatomic particle that has no charge and that is found in the nucleus of an atom
negatively charged particle; located outside the atomic nucleus
atomic (proton) number
The number of protons present in the nucleus of all atoms of one particular element.
mass (nucleon) number
The combined total of neutrons and protons in the nucleus of one particular isotope of an element.
atoms of the same element that have different numbers of neutrons
the process by which an unstable nucleus gives off nuclear radiation
radioactive decay that results in an alpha particle (a helium nucleus) being emitted from the nucleus of a radioactive element.
beta minus decay
A neutron is converted into a proton, an electron. The electron is released as a beta particle.
the release of gamma rays from a nucleus.
Made up of 2 protons and 2 neutrons.
an electron emitted by an unstable nucleus.
are stopped by paper or skin.
are stopped by a thin sheet of aluminium foil.
are stopped by lead or thick layer of concrete.
is the most ionizing but the least penetrating.
is the least ionizing but the most penetrating.
length of time required for half of the radioactive atoms in a sample to decay.
element used in dating organic material.
Radioactive material (γ-emitters) which are ingested into the body. Must have a long enough half-life to carry out investigation but no longer.
is monitored by passing beta particles through the paper when it is manufactured.
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