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Properties and Uses of Radiation from Unstable Isotopes Chemistry Tutorial

Key Concepts

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Properties of Radiation

Henri Becquerel discovered radioactivity in 1896.1

A few years later, Ernest Rutherford found 2 distinct types of radiation from uranium:

In 1900, Villard identified a third radiation from radium. This radiation was much more penetrating than alpha and beta, and he called it gamma radiation (γ).

Experiments looking at how these radiations interact with magnetic fields and electrically charged plates indicated that:

Alpha-particles (α-particles) have more mass than beta-particles (β-particles).
Gamma rays (γ-rays) have no mass, they are part of the electromagnetic spectrum.

The identity of each type of radiation is known to be:

The most dangerous form of radiation to living things are gamma rays (γ-rays) because they have the greatest penetrating power and are the most energetic. Gamma-rays (γ-rays) can penetrate the tissue of living organisms and are therefore useful in sterlisation because they kill bacteria.
Less energetic beta particles (β-particles) can also be harmful if they come into contact with living things, burning skin.
Less energetic alpha particles (α-particles) can be harmful if ingested.

The properties of alpha, beta and gamma radiation are summarised in the table below:

Name Symbols Identity Relative Charge Relative Mass Penetrating Power Interaction with Charged Plates Hazards
alpha α

4 He

2+ 4


Stopped by a sheet of paper

⚛ Attracted to negative plate.
⚛ Deflected by positive plate.
Harmful if ingested
beta β

0 e

electron 1-     1    


Passes through paper and ½ mm aluminium.
Stopped by ½ mm lead.

⚛ Attracted to positive plate.
⚛ Deflected by negative plate.
Skin burns.
Harmful if ingested, particularly iodine-131 in thyroid and strontium-90 in bones.
gamma γ electro-
0 0


Only stopped by several centimetres of lead or many centimetres of concrete.

Unaffected Most dangerous as these are the most penetrating, as a consequence, gamma rays can be used to sterilize materials and destroy bacteria in food.

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Uses of Radioisotopes

All the elements beyond bismuth (Bi) in the Periodic Table of the Elements display radioactivity.
There are natually occurring radioactive isotopes of many of the other elements as well.

Naturally occurring radioisotopes can be used to date :

Radioisotopes that emit low-penetrating alpha particles and that have a relatively long half-life have found use in domestic settings such as smoke detectors.

To be useful, radioisotopes with very short half-lives, such as those measured in seconds, hours, or days, are produced in nuclear reactors or cyclotrons close to the where they will be used.
These are man-made, or synthetic, radioisotopes.
These radioisotopes are particularly useful in medical applications.
A short half-life, such as a few hours, means that the radiation is reduced to harmless levels quickly.
A longer half-life, such as hundreds or thousands of years, means that the radioisotope continues to emit harmful radiation for a very long period of time.

The table below gives the emitted radiation, half-life, and uses for a selection of useful isotopes in order of decreasing half-life.

Isotope Radiation Emitted Half-life Use
Oxygen-18 stable   Biological tracer
for example, in studies of photosynthesis
Rubidium-87 beta 48 × 109 years Rubidium-Strontium radiometric dating
(millions of years)
Uranium/Lead U-238 alpha & gamma 4.5 × 109 years Radiometric dating
(millions to billions of years)
Potassium-40 positron emission 1.26 × 109 years Potassium-Argon radiometric dating
(100 000 to several billion years)
Uranium-235 alpha, gamma 7.1 × 108 years Enriched as a fuel for most nuclear reactors
Chlorine-36 beta 3.01 × 105 years Measurement of sources of chloride and determining the age of water up to about 2 million years old.
Naturally occurring radioisotope.
Plutonium-239 alpha, gamma 24 400 years Fuel for most "fast-breeder" nuclear reactors
Carbon-14 beta 5 730 years Radiometric dating
Determination of age of carbon-containing artifacts up to about 70,000 years.
Also used as a biological tracer, for example, in studies of photosynthesis.
Naturally occurring radioisotope.
Americium-241 alpha 432 years Domestic smoke alarms and neutron gauging.
Americium-241 is a decay product of plutonium-241 formed in nuclear reactors.
Caesium-137 beta 30.2 years Radiotracing to identify sources of soil erosion and depositing.
Also used in thickness gauging.
Lead-210 beta 22.3 years Date layers of soil and sand deposited up to about 80 years ago.
Naturally occurring radioisotope.
Tritium beta 12.32 years Measure the age of 'young' groundwater up to about 30 years old.
Naturally occurring radioisotope.
Titriated water is used to study sewage and liquid wastes.
Cobalt-60 beta, gamma 5.3 years Cancer treatment as tumour cells tend to be more susceptible to radiation than other cells.
Manganese-54 gamma 312.2 days Used to predict the behaviour of heavy metals in effluents from mining waste water.
Zinc-65 gamma 244.26 days Used to predict the behaviour of heavy metals in effluents from mining waste water.
Gadolinium-153 gamma 240.4 days Used in X-ray fluorescence and bone density guages for osteoporosis screening.
Iridium-192 beta 73.83 days Supplied as a wire for use as an internal radiography device.
Iron-59 beta, gamma 46.3 days Used in blood studies.
When incorporated into steel it is used to determine the amount of friction in machinery.
Chromium-51 alpha 27.7 days Labelling of red blood cells and quantifying gastro-intestinal protein loss.
Isotope prepared in a nuclear reactor.
Phosphorus-32 beta 14.28 days Treatment of excess red blood cells.
Isotope prepared in a nuclear reactor.
Iodine-131 beta, gamma 8.1 days Medical tracer to study and treat the thyroid gland.
Used in the diagnosis of adrenal medullary and for imaging suspected neural crest and other endocrine tumours.
Isotope prepared in a nuclear reactor.
Gallium-67 gamma 3.3 days Tumour-seeking agent.
Isotope prepared in a cyclotron.
Thallium-201 gamma 3 days Locating damaged heart muscle.
Isotope prepared in a cyclotron.
Ytterbium-169 gamma 3 days Brain scans.
Isotope prepared in a nuclear reactor.
Molybdenum-99 beta 2.75 days Used as the 'parent' in a generator to produce technetium-99m, the most widely used radioisotope in nuclear medicine.
Isotope prepared in a nuclear reactor.
Gold-198 beta 2.69 days Trace factory waste causing ocean pollution and to trace sand movement in river beds and on ocean floors.
Yttrium-90 beta 2.67 days Liver cancer therapy.
Isotope prepared in a nuclear reactor.
Samarium-153 beta 1.93 days Used in the treatment of pain associated with bony metastases of primary tumours.
Isotope prepared in a nuclear reactor.
Potassium-42 beta & alpha 22 hours Determination of exchanged potassium in blood flow.
Isotope prepared in a nuclear reactor.
Sodium-24 beta, gamma 15 hours Location of leaks in water pipes, studies of body electrolytes.
Isotope prepared in a nuclear reactor.
Iodine-123 gamma 13.2 hours Used in imaging to monitor thyroid function and detect adrenal dysfunction.
Isotope prepared in a cyclotron.
Copper-64 gamma 12.7 hours Dtudying genetic disease affecting copper metabolism.
Isotope prepared in a nuclear reactor.
Technetium-99 beta 6 hours Medical tracer used to locate brain tumours and problems with the lungs, thyroid, liver, spleen, kidney, gall bladder, skeleton, blood pool, bone marrow, salivary and lacrimal glands and heart blood pool and to detect infection.
Isotope prepared in a nuclear reactor.
Magnesium-27 beta, gamma 9.5 minutes Location of leaks in water pipes.
Krypton-81 gamma 13 seconds Lung ventilation studies.
Isotope prepared in a cyclotron.

Positron emitters such as carbon-11, nitrogen-13, oxygen-15 and fluorine-18 are produced in a cyclotron and are extremely short lived isotopes.
They are used in positron emission tomography (PET) for studying brain physiology and pathology for epilepsy and dementia.

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1. Henri Becquerel discovered X-rays a year earlier, in 1985.

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