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48 Cards in this Set
- Front
- Back
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Who devised the experiment that changed the way we thought of the atom in 1911?
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Ernest Rutherford
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Who carried out the experiment that changed the way we thought of the atom in 1911?
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Geiger and Marsden – two research students working for Rutherford.
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What was the outcome of the Rutherford (Geiger and Marsden) scattering experiment?
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A change in the scientific thinking of what the atom's structure is like.
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What was the target in the Rutherford (Geiger and Marsden) experiment?
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Very thin gold foil (so it was only a couple of atoms thick).
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What was fired at the gold foil in the Rutherford (Geiger and Marsden) experiment?
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Alpha particles
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Why was the gold foil fired at in a vacuum in the Rutherford (Geiger and Marsden) experiment?
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Air would have absorbed the alpha particles before they reached the gold foil
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How was the path of the alpha particles detected in the Rutherford and Marsden experiment?
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When the alpha particles hit a zinc sulphide screen a flash of light was seen.
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What was the model of the atom that preceded the nuclear model?
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The ‘plum pudding’ model of the atom.
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What were the findings of the Rutherford Geiger and Marsden) experiment
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Most of the alpha particles went straight through the gold foil or were deflected a tiny bit (as expected) but about 1 in 8000 were backscattered – deflected by more than 90 degrees
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What was concluded from the Rutherford and (Geiger and Marsden) experiment?
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That the atom had a dense, small, positively charged nucleus orbited by electrons so it is neutral overall and most of the atom is empty space
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What was the 'plum pudding' model like?
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A sphere of positive charge with negative charges embedded in it - like currants in a Christmas plum pudding.
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What is the nuclear model of the atom like?
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A tiny, dense, positive nucleus with negative electrons orbiting it (like the planets orbiting the Sun)
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What is the mass of a proton (in atomic mass units)?
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1u (at GCSE)
At A level we have to use mass in kg from the data sheet |
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What is the mass of a neutron (in atomic mass units)?
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1u
At A level we have to use mass in kg from the data sheet |
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What is the mass of an electron (in atomic mass units)?
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Negligible to that of the proton or neutron - 0.00055u - NEVER say it is zero!
At A level we have to use mass in kg from the data sheet |
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What is the charge of a proton?
(in relative atomic charge units NOT coulombs) |
+1 (no unit is necessary here)
At A level we have to use charge in coulomb from the data sheet |
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What is the charge of a neutron?
(in relative atomic charge units NOT coulombs) |
zero
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What is the charge of an electron?
(in relative atomic charge units NOT coulombs) |
-1 (no unit is necessary here)At A level we have to use charge in coulomb from the data sheet
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What is the charge on an atom if the number of electrons is equal to the number of protons in the nucleus?
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The atom has no net electrical charge.
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What is an atom called that loses or gains electrons?
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An ion.
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What is significant about the number of protons in the nucleus?
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All atoms of a particular element have the same number of protons.
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What is an isotope?
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Atoms of the same element (therefore having the same number of protons as each other) which have different numbers of neutrons are called isotopes.
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What is atomic number?
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The total number of protons in an atom's nucleus is called its atomic number.
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What is the mass number?
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The total number of protons and neutrons in an atom's nucleus is called its mass number.
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What is an alpha particle?
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Two protons and two neutrons (a helium nucleus) that comes out of a nucleus.
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What is a beta particle?
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A fast electron that comes out of the nucleus.
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What is a gamma ray?
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High energy electromagnetic radiation.
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Does losing a gamma ray change the particles in the nucleus?
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No, it is still the same nucleus - it is just at a lower energy level.
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What happens when a nucleus loses an alpha particle?
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The nucleus loses two protons (therefore becoming a nucleus of a different element) and two neutrons.
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What happens when a nucleus loses a beta particle?
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The nucleus loses a neutron and gains a proton (therefore becoming a nucleus of a different element). The neutron has emitted a beta particle (losing negative charge and becoming positive).
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Where does artificial background radiation come from?
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Nuclear weapons and testing and nuclear power plants - medical uses.
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Where does natural background radiation come from?
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Cosmic rays, natural radioactive isotopes in the rocks and atmosphere - from there in food etc too - mainly (50%) radon in the atmosphere.
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What is nuclear fission?
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The splitting of atomic nuclei (speak of the nucleus splitting not the atom!)
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How many parts does the nucleus split into?
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Two
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What else is produced besides the two fission fragments?
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Besides the two smaller nuclei 2 or 3 neutrons are also released.
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What is nuclear fission used for?
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It is used in nuclear reactors as a source of heat energy which can be transformed to electrical energy.
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What is nuclear fusion?
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It is the joining together of two small atomic nuclei into one big nucleus. (Talk of nuclei not atoms!).
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What is nuclear fusion used for?
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It is the process by which energy is released in stars. We are trying to create fusion reactors but haven't done it yet.
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Name the two fissionable substances in common use in nuclear reactors.
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Uranium 235 and Plutonium 239.
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What is induced fission?
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When we start the fission process off (like induced births...)
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What type of fission occurs with uranium 235 or plutonium 239?
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Induced fission - the nucleus must first absorb a neutron to start the process off.
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Why does a chain reaction occur?
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The neutrons released may go on to cause another fission which in turn releases more neutrons that then cause more fissions and so on. This is called a chain reaction.
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What is the process by which energy is released in stars?
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Nuclear fusion.
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Which process (fusion or fission) releases the most energy per kilogram?
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Fusion
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What slows neutrons down?
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Graphite moderator (moderates the speed of neutrons so they are more likely to be absorbed by the uranium nucleus)
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What absorbs neutrons?
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Boron control rods
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What is nuclear fuel?
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Pellets of enriched uranium or plutonium are put into fuel rods.
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Why is thick concrete shielding necessary around a nuclear reactor?
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Radioactive isotopes give out alpha, beta and gamma rays - gamma rays are very penetrating so a thick dense barrier needs to be put around it.
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