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An atom of any given element consists of a nucleus containing a
number of protons and neutrons. The nucleus is surrounded by
The halflife of a radioactive isotope is the time taken for half its
radioactive atoms to decay.
There are three main types of radiation, called alpha, beta and
gamma radiation, which all have different properties. Radiation can
damage cells and make them cancerous. Very high doses of
radiation can kill cells. It can be detected using photographic film or
a GeigerMuller tube. Radiation badges are used to monitor the
level of radiation that people who work with radioactive sources are
exposed to.
Radiation has many practical uses. It can be used in medicine to
trace where certain chemicals collect in the body, indicating
disease, and also in industry, where it can be used to control
measuring equipment.
Atoms and isotopes
The nuclear model
Structure of the atom
Atoms contain three subatomic particles called protons, neutrons and
electrons. The protons and neutrons are found in the nucleus at the centre
of the atom, and the electrons are arranged in energy levels or shells
around the nucleus.
All the atoms of a given element have the same number of protons and
electrons. However, the number of neutrons can vary. Atoms of the same
element that have different numbers of neutrons are called isotopes of that
element. The diagram shows three hydrogen isotopes.

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1 proton, 0 neutron, 1 electron
1. Back
2. 1
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The different isotopes of an element have identical chemical properties.
Some isotopes, however, are radioactive. This means that they give out
radiation from their nuclei. This happens all the time, whatever is done to
the substance. For example, the radiation is still given out if the substance
is cooled down in a freezer, or takes part in a chemical reaction.…read more


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