IGCSE Physics definitions Topic 5 (Atomic Physics) – Flashcards
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NUCLEUS
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The centre of the atom that contains most of the mass of the atom. The nucleus is positively charged. Negative electrons orbit the nucleus
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NUCLIDE
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A general word for the nucleus of any element
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RADIOACTIVITY
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The spontaneous and random release of energy and particles from unstable nuclei such as Uranium
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BACKGROUND RADIATION
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The radiation that is always present around us. It may be from natural or man - made sources
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ALPHA PARTICLES
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Alpha particles are made of 2 protons and 2 neutrons. They are emitted from radioactive nuclei. Alpha particles are positively charged and large so they are deflected by electric and magnetic fields
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BETA PARTICLES
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Beta particles are electrons emitted from radioactive nuclei. Beta particles are negatively charged and small so they are deflected by electric and magnetic fields
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GAMMA RAYS
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These are high energy electromagnetic waves emitted from unstable radioactive nuclei. Gamma rays do not have electric charge or mass so they are not deflected by electric and magnetic fields
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IONISATION:
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Occurs when radiation knocks out electrons from neutral atoms and leaves them with a positive charge
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HALF LIFE
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The time taken for half the original nuclei to decay. Or the time for half the mass to decay - which is the same {Unit: s}
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PROTON NUMBER
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The number of protons in the nucleus
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NUCLEON NUMBER
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The total number of protons AND neutrons in the nucleus
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ALPHA SCATTERING EXPERIMENT
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Alpha particles aimed at a thin metal foil. Some bounced back. Proved the existence of the nucleus and that it is small, massive with positive charge.
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ISOTOPES
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Elements with the same number of protons in the nucleus but different number of neutrons
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USES OF RADIOACTIVE ISOTOPES
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To kill cancer cells. To sterilize food (gamma rays). To follow movement of pollution (beta radiation). Fire alarms (alpha particles)
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RADIOACTIVE DECAY EQUATIONS
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When alpha or beta particles are emitted from the nucleus, the number of protons and neutrons in the nucleus changes so a new element is made
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SAFE HANDLING OF RADIOACTIVITY
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Do not point radioactive sources at people. Wear gloves. Use shields eg lead. Keep radioactive sources in a locked room
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Nuclear fission
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This is where a large nucleus such as uranium is split into 2 pieces and releases energy. Used in power stations and atomic bombs
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Nuclear fusion
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This is where small nuclei eg: Hydrogen are forced together and so release energy. Thus is the energy source of the sun and stars
