Properties of Nuclei and the Nuclear Force · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Tiny cores, enormous densities

Science · Quantum & Modern Physics · ages 19-21
Name ______________________   Date ____________

  1. What is the range of the strong force?

    • Across the whole atom
    • A few femtometers, then it fades
    • Infinite, like gravity

  2. What does A count in a nucleus?

    • Protons plus neutrons
    • Protons only
    • Electrons in shells

  3. Where does binding energy per nucleon peak?

    • Near the lightest gases
    • At the heaviest elements
    • Near iron

  4. Mirror nuclei swap proton and neutron counts yet bind nearly alike. What does that show?

    • Protons repel neutrons strongly
    • The strong force is nearly charge blind
    • Neutrons carry positive charge

  5. A nucleus has nucleon number 8. Type its radius in fm.

    Answer: ______________

  6. Why do heavy nuclei carry extra neutrons?

    • Extra neutrons dilute the proton repulsion with short range glue
    • Neutrons cancel electron charge
    • Protons decay without neutrons

  7. Lead and helium nuclei differ hugely in size, yet their densities match. Why?

    • Lead has no neutrons
    • Helium nuclei are hollow
    • Volume scales with nucleon number, so density stays flat

  8. Fusing two light nuclei into a heavier one near iron releases energy.

    Circle one:   True   False

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Answer key

For grown-ups. Fold this page away before handing over the rest.

Tiny cores, enormous densities W1-mt_HdMS_muGWa-s1

  1. A few femtometers, then it fades · The strong grip spans a few femtometers before repulsion takes over.
  2. Protons plus neutrons · A is the mass number: every nucleon, proton or neutron.
  3. Near iron · The curve climbs to iron and falls past it.
  4. The strong force is nearly charge blind · Swapped counts binding alike means the grip ignores charge.
  5. 2.4 · The cube root of 8 is 2, and 1.2 times 2 is 2.4 fm.
  6. Extra neutrons dilute the proton repulsion with short range glue · Extra neutrons add attraction without adding repulsion.
  7. Volume scales with nucleon number, so density stays flat · Volume grows with A, keeping the packing density nearly constant.
  8. True · Binding per nucleon climbs toward iron, and the gain leaves as released energy.
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