5.3.1 THE NUCLEAR ATOM

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Describe the set up of the alpha scattering experiment
source/ gold foil/ moveable detector/ 2+ trajectories/ vacuum
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Describe the results of the alpha scattering experiment
most particles little or any deflection/ large deflection of very few (more that 90)/ elastic scattering/ alpha particle repelled by + nucelsu
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what were rutherford's conclusions from the alpha scattering experiment?
most particles went straight through - atom mostly empty space/ some alpha ps deflected more than 90 - centre of atom must be tiny but dense/ A particles repelled - nucleus must be +/ atoms neutral overall - electrons must be on the outside of atoms
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Define nucleon number
total sum of protons and neutrons in the nucleus/
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Define proton number
number of protons found in the nucleus
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What is the diameter of a nucleus? Describe the nucleus
10-14m/ made up of nucleons/ protons and neutrons have similar densities - same vol and dense
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What is an isotope?
atoms with the same number of protons and electrons but a different number of neutrons
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Describe the characteristics of isotopes of elements
affect the stability of a nucleus/ unstable nuclei may be radioactive
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Name the forces present within a nucleus
electrostatic/ gravitational and strong nuclear
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Describe the electrostatic forces in a nucleus
all protons have equal positive charge, packed closely will repel/ neutral between neutrons/ long range/ bigger than gravitational
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Describe the gravitational forces in a nucleus
effective is very small/ newton says that two massive objects will attract each other/ attractive/ long ranged/ inverse square law/ use gravitational theory equation
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Describe the strong nuclear force
binds nucleons together/ attractive force greater than electrostatic/ only attractive over short range then become increasingly repulsive (other wise it would collapse)
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What causes a nucleus to decay?
too many neutrons/ too few neutrons/ too many nucleons (too heavy)/ too much energy
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Describe alpha decay
heavy nuclei/ one helium nuclei emitted/ nucleon n decreases by 4 and proton decreases by 2/ only with protons numbers bigger than 82, too big to be stable
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Describe the two types of beta emission
beta minus when lots of electrons/ beta plus when lots of protons
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describe beta minus decay
electron is beta particle/ also relates antineutrino/ one neutron turns into a proton and an electron + anti neutrino/ proton number INCREASES BY 1
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describe beta plus decay
beta particle is positron and neutrino/ proton turns into these/ PROTON N DECREASES BY 1
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Describe gamma ray emission
nuclei with too much energy/ no change in nucleons, just loses energy
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What quantities are conserved in nuclear decay?
charge/ total n of protons and neutrons/ energy/ momentum of system/ lepton number
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What quantities are not conserved in nuclear decay?
mass/ mass of nucleus is less than its constituents - mass defect/ e=mc2 mass and energy are equivalent/ energy released when the nucleons bonds together accounts for missing mass
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Describe the mass defect
e=mc2/ energy released = mass defect x c2// was of system increases when external energy is supplied/ ENERGY IS RELEASED FROM SYSTEM IS MASS INCREASES
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Describe how the strong nuclear force between nucleons is attractive and short ranged
protons do not move apart even though electrostatic force is much greater than gravitational/ must be short ranged attractive force
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Card 2

Front

Describe the results of the alpha scattering experiment

Back

most particles little or any deflection/ large deflection of very few (more that 90)/ elastic scattering/ alpha particle repelled by + nucelsu

Card 3

Front

what were rutherford's conclusions from the alpha scattering experiment?

Back

Preview of the front of card 3

Card 4

Front

Define nucleon number

Back

Preview of the front of card 4

Card 5

Front

Define proton number

Back

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