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26 Cards in this Set
- Front
- Back
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What is the main source of radioactivity? Name three other sources of radioactivity. |
Radon gas (50%)
Any of: Ground and buildings, medical, food and drink, cosmic rays, nuclear waste |
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What is radioactivity measured in? |
Becquerels |
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What is 1 Becquerel equal to? |
1 count/ disintegration per second |
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What identifies an element? |
The number of protons |
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What is an isotope? |
An atom with the same number of protons but different numbers of neutrons. |
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Why do unstable nuclei decay? |
The strong nuclear force of an atom holds the atom together, and stops the protons in the nucleus repelling the electrons away. If an atom is unbalanced (too many or few neutrons) or too big, it will start to split apart. |
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What is an alpha particle? What stops it? How strong is it? |
A helium nucleus (2 protons and 2 neutrons) Paper Low penetrating power but highly ionising |
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What is a beta particle? What stops it? How strong is it? |
An electron Aluminium Medium penetrating power and ionising strength |
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What is gamma radiation? What stops it? How strong is it? |
Electromagnetic wave Thick lead Weak ionising strength but high penetrating power |
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Which radioactive decay particle/wave travels furthest? Shortest? |
Gamma travels furthest (virtually infinite) Alpha travels shortest (about 10cm) Beta travels about 1 metre |
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Describe alpha decay. |
-The amount of neutrons and protons in the atom is unbalanced -The strong nuclear force is disturbed -Alpha particles are 'kicked out' of the atom until the atom becomes stable |
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What happens to the atomic and mass numbers of the element that decays in alpha decay? |
The mass number will decrease by 4 and the atomic number will decrease by 2 |
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Describe beta decay. What happens to the mass and atomic numbers of the element? |
-A neutron in the nucleus turns into a proton and an electron -The electron is emitted from the nucleus -The mass number is the same, the atomic number increases by 1 (as there is another proton in the nucleus) |
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What is background radiation? |
the radioactive particles hitting us all the time from radioactive sources on earth and in space |
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What is actual count? |
Measured count - background radiation |
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What measures radioactivity? |
A Geiger-Muller tube |
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What is a half life? |
The average time taken for half of the original activity of a sample to decay |
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Describe the plum pudding model of an atom. |
-Equally distributed mass -Electrons randomly placed in a sphere of positive charge |
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Describe the Rutherford scattering experiment. What did he expect? |
-Rutherford fired alpha particles at gold foil -He expected most particles to go through with small deviation (as alpha particles are positive) |
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What actually happened? What were the conclusions? |
-Most alpha particles went straight through: most of the atom is empty space -Some particles were deflected at large angles: there is a concentrated positive mass in the atom -A small number were deflected backwards: the mass of the atom is concentrated in the nucleus |
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Give 3 applications of radioactivity. |
Medical tracers Sterilization Seeing how thick a metal is Cancer treatment X rays Carbon dating Gauging the flow of liquids |
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Describe the process of nuclear fission. Include chain reaction. |
-A neutron hits and is absorbed by an unstable atom. The neutron cannot be travelling too fast -The atom splits into 2 daughter nuclei, three neutrons, gamma radiation and kinetic energy -These neutrons can strike more atoms -If there is enough of the radioactive material- critical mass- a chain reaction occurs and huge amounts of energy are released very quickly
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What is the waste product of nuclear fission? What is this used for? |
Plutonium Nuclear weapons |
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What does the moderator (in a nuclear generator) do? What is it made out of? |
The moderator slows the neutrons down, making them more easily absorbed by the uranium/radioactive material. Graphite |
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What do the control rods (in a nuclear generator) do? What are they made out of? |
Control rods absorb excess neutrons, making sure the reaction does not get out of control. Boron |
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How does a nuclear generator produce electricity? |
The moderator gets hot from the energy. This heat is used to heat water, which makes steam, which turns a generator, which makes electricity. |
