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Radioactivity: 4. Properties & hazards of ionizing radiation: alpha, beta & gamma
4. Alpha, Beta & Gamma Radiation Properties and dangers of atomic-nuclear-ionising radiation
Sub-index for this page 4a. Detailed properties of the three types of radioactive emission and symbols 4b. Dangers of radioactive emissions - beware of ionising radiations from radio-isotopes Appendix 1. Explaining the effect of ionizing radiations on atoms & molecules Note there is a separate page for ... uses of radioactive Isotopes emitting alpha, beta or gamma radiation AND Appendix 2 is an extra advanced physics section which most students do NOT need, just did it for my own interest RADIOACTIVITY and NUCLEAR PHYSICS NOTES INDEX IGCSE/GCSE/O Level Physics & Chemistry revision notes on Radioisotopes - this page describes the properties of alpha particle radiation, beta particle radiation and gamma radiation in terms of their charge, mass, penetration of materials, behaviour in an electric field, their relative ionising capacity and the dangers of ionising radiation from both external radioactive sources and internally ingested radionuclide. These revision notes on the properties of alpha, beta and gamma ionising radiation and their dangers should help with IGCSE/GCSE/ chemistry or physics courses and A/AS advanced level chemistry or physics courses. |
4a. The Properties of the three types of Radioactive Emission and symbols IONISING RADIATIONS emitted when unstable atomic nuclei undergo radioactive decay
REMINDER: Experiment to show there are at least three types of emissions from radioactive substances. Left to right - alpha particles, gamma rays and beta particles
The PROPERTIES of ALPHA, BETA, GAMMA and neutron RADIATIONS
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Type of radiation emitted & symbol |
Nature of the radiation formation, structure, relative mass, electric charge |
Other nuclear Symbols |
Penetrating power (and speed), and what will block it (more dense material, more radiation is absorbed BUT smaller mass or charge of particle, more penetrating). |
Ionising power - the ability to remove electrons from atoms to form positive ions, the process is called ionisation |
Alpha particle radiation |
a helium nucleus of 2 protons and 2 neutrons, mass = 4, charge = +2, is expelled at high speed from the nucleus |
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Low penetration, slowest speed (but still ~10% speed of light!), biggest mass and charge, stopped by a few cm of air or thin sheet of paper, so obviously will be stopped by a few cm layer of concrete, sheets of aluminium or lead. |
Very high ionising power, the biggest mass and charge of the three radiation's, the biggest 'punch' in ripping off electrons from molecules, other ions are formed |
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high kinetic energy electrons, mass = 1/1850, charge = -1, expelled when a neutron changes to a proton in the nucleus |
beta minus, beta |
Moderate penetration (~90% speed of light), 'middle' values of charge and mass, most stopped by a few mm of metals like aluminium, will travel quite a few metre in air, will be stopped by a few cm layer of concrete, sheets of lead. |
Moderate ionising power, with a smaller mass and charge than the alpha particle, but still quite good at knocking off electrons from molecules - moderate ionisation |
Gamma radiation |
very high frequency electromagnetic radiation, mass = 0, charge = 0, gamma emission often accompanies alpha and beta decay |
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Very highly penetrating (100% speed of light !), smallest mass and charge and greatest speed, most stopped by a thick layer of steel or a very thick layer of concrete, but even a few cm of dense lead doesn't stop all of it! Gamma rays can pass through many m of air. It takes many m of concrete plus steel to absorb it all. |
The lowest ionising power of the three, gamma radiation carries no electric charge and has virtually no mass, so not much of a 'punch' when colliding with an atom to remove an electron, weak ionisation |
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high KE positive electron called a positron, mass = 1/1850, charge = +1, expelled when a proton changes to a neutron in the nucleus. |
![]() beta plus, beta + |
The positron is the antiparticle of the electron. it is identical to an electron but opposite in charge. It is rapidly destroyed when it meets any electron (see on right) producing two high energy gamma ray photons, so it doesn't get very far! The co-destruction of particle and anti-particle is called annihilation! The effect is used in PET scanning in medicine. |
Theoretically as above, BUT when electron meets positron, kapow !
e+ + e
==> 2
equation for annihilation ! |
n neutron radiation |
neutron, mass = 1, charge = 0, fundamental particle of the nucleus |
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Highly penetrating (more than alpha & beta & sometimes gamma). However, neutrons are most readily absorbed by light nuclei so hydrogen-rich materials like water, poly(ethene) plastic and concrete are used for neutron radiation shielding. The nuclei formed often emit gamma radiation so an extra thick protective layer of lead is needed around a neutron rich environment ! |
Can't ionise directly, but they are absorbed by the nuclei of atoms they pass through. This can make the atom unstable - radioactive, hence other nuclear radiations may then be produced, producing an 'indirect ionisation' effect. So neutron radiation is as dangerous as any of the others. |
The penetration properties of the three radiations
Two simple diagrams (above & below) to show the penetration of alpha particle radiation, beta particle radiation and gamma radiation (for more details see the table below).
IMPORTANT NOTE:
Nuclear-atomic radiation - usually called ionising radiation:
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Beware of ionising radiations from radioisotopes! The penetration trends and the effects of Ionisation from radioisotopes
Appendix 1. Explaining the effect of ionizing radiations on atoms & molecules (a) Excitation of atoms by absorbing EM radiation which then give out (emit) EM radiation
(b) The complete ionisation of an atom
Note on the use of fluorescence tubes for lighting
and
What next? Associated Pages RADIOACTIVITY and NUCLEAR PHYSICS NOTES INDEX See also Electromagnetic radiation, types, properties, uses and dangersGCSE Level (~US grade 8-10) School Physics Notes (students age ~14-16) GCSE Level (~US grade 8-10) School Chemistry Notes (students age ~14-16) Find your GCSE science course for more help links to revision notes ALL my Advanced Level pre-university Chemistry Notes (students aged ~17-18) This is a BIG website, you need to take time to explore it [ SEARCH BOX]Use your mobile phone in 'landscape' orientation? Email doc brown - comment? query Atomic structure, radioactivity and nuclear physics revision notes index Atomic structure, history, definitions, examples and explanations including isotopes 1. Atomic structure and fundamental particle knowledge needed to understand radioactivity 2. What is Radioactivity? Why does it happen? Three types of atomic-nuclear-ionising radiation 3. Detection of radioactivity, its measurement and radiation dose units, ionising radiation sources - radioactive materials, background radiation 4. Alpha, beta & gamma radiation - properties of 3 types of radioactive nuclear emission & symbols ,dangers of radioactive emissions - health and safety issues and ionising radiation 5. Uses of radioactive isotopes emitting alpha, beta (+/) or gamma radiation in industry and medicine 8. Nuclear fusion reactions and the formation of 'heavy elements' by bombardment techniques 9. Nuclear Fission Reactions, nuclear power as an energy resource
RADIOACTIVITY multiple choice QUIZZES and WORKSHEETS Easier Foundation Tier Radioactivity multiple choice QUIZ Harder Higher Tier Radioactivity multiple choice QUIZ Worksheet QUIZ Question 1 on RADIOACTIVITY - absorption of alpha, beta and gamma radiation Worksheet QUIZ Question 2 on RADIOACTIVITY - dangers & monitoring ionising radiation levels Worksheet QUIZ Question 3 on RADIOACTIVITY - revision of atomic structure Worksheet QUIZ Question 4 on RADIOACTIVITY - what happens to atoms in radioactive decay? Worksheet QUIZ Question 5 on RADIOACTIVITY - uses of radioisotope and half-life data ANSWERS to the WORD-FILL WORKSHEET QUIZZES Crossword puzzle on radioactivity and ANSWERS!
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