Atomic and nuclear physics flashcards

Atomic and nuclear physics covers the structure of the atom, from the nuclear model with a dense positive nucleus surrounded by electrons, to the quantum idea of discrete energy levels. Students must understand radioactive decay, including alpha, beta-minus, beta-plus and gamma radiation, along with half-life and decay equations. Nuclear reactions require knowledge of mass-energy equivalence using E = mc^2, binding energy per nucleon, and how fission and fusion release energy. The strong nuclear force holds nucleons together against electrostatic repulsion. Students should be able to interpret nuclear equations, use N = N0 x (1/2)^(t/t½), and explain why nuclei with certain proton-to-neutron ratios are unstable. Radioactive decay is a random and spontaneous process, and activity is proportional to the number of undecayed nuclei present.

1. Card 1

   What is the nuclear model of the atom?

   A tiny, dense, positively charged nucleus contains protons and neutrons, with electrons occupying the space around it. Most of the atom is empty space.

2. Card 2

   What is meant by the atomic number and mass number of a nucleus?

   Atomic number (Z) is the number of protons; mass number (A) is the total number of protons and neutrons (nucleons) in the nucleus.

3. Card 3

   What are isotopes?

   Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons, giving them different mass numbers.

4. Card 4

   What are the properties of alpha radiation?

   An alpha particle is two protons and two neutrons (helium-4 nucleus). It is highly ionising, travels a few centimetres in air, and is stopped by paper or skin.

5. Card 5

   How does beta-minus decay occur and what is emitted?

   A neutron converts to a proton, emitting a fast electron (beta-minus particle) and an antineutrino. The atomic number increases by one.

6. Card 6

   What is gamma radiation and how does it differ from alpha and beta?

   Gamma radiation is a high-energy electromagnetic wave with no charge or mass. It is the least ionising but most penetrating, requiring thick lead or concrete to absorb it.

7. Card 7

   Define half-life and state the decay equation.

   Half-life (t½) is the time for half the undecayed nuclei to decay. The equation is N = N0 x (1/2)^(t/t½), where N0 is the initial number of nuclei.

8. Card 8

   Why is radioactive decay described as random and spontaneous?

   Random means it is impossible to predict which nucleus decays next; spontaneous means decay is not triggered by external conditions such as temperature or pressure.

9. Card 9

   What is binding energy and what does it tell us about nuclear stability?

   Binding energy is the energy needed to completely separate all nucleons. Higher binding energy per nucleon means a more stable nucleus; iron-56 has the highest value.

10. Card 10

    How does E = mc^2 apply to nuclear reactions?

    The mass defect (difference between reactant and product masses) converts to energy via E = mc^2, explaining the energy released in fission and fusion reactions.

11. Card 11

    Why does nuclear fusion release energy for light nuclei but fission releases energy for heavy nuclei?

    Both processes move nuclei towards iron-56, the peak of the binding energy per nucleon curve. Light nuclei gain stability by fusing; heavy nuclei gain it by splitting.

12. Card 12

    What is the strong nuclear force and why is it needed?

    The strong nuclear force is a short-range attractive force between nucleons that overcomes electrostatic repulsion between protons, keeping the nucleus together.

• Students often confuse activity (decays per second) with the number of undecayed nuclei, forgetting that activity decreases as nuclei are used up and is always proportional to N.
• A common error is thinking that after two half-lives a sample has completely decayed, rather than understanding that one quarter of the original nuclei remain undecayed.
• Many students incorrectly apply mass-energy equivalence by using the total mass rather than the mass defect, so they calculate the total rest energy of the nucleus instead of the energy released in the reaction.

Planning your revision? Read how to revise IB Physics, or make cards from your own notes with the notes to flashcards tool.