SP6 Flashcards
(18 cards)
What replaced the plum pudding model?
Rutherford’s nuclear model (gold foil experiment, fired alpha particles at thin gold sheet)
What did the gold foil experiment show?
Most alpha particles passed through (atom mostly empty space), some deflected (positive nucleus)
What are the relative masses of protons, neutrons, electrons?
Proton: 1, Neutron: 1, Electron: ~0 (1/1837)
What is the atomic number?
Number of protons (also electrons if neutral)
How do electrons move between energy levels?
Absorb energy → jump up; emit energy as light → fall down
What is ionisation?
Electron removed completely (requires enough energy)
What is β⁻ decay?
Neutron → proton + electron (ejected as β particle)
Definition of half-life:
Time for half the radioactive nuclei to decay
A sample decays from 200g to 25g in 60 years. What is its half-life?
200 → 100 → 50 → 25 (3 half-lives). 60 ÷ 3 = 20 years
Medical uses of radiation:
Tracers (γ emitters like technetium-99).
Radiotherapy (γ rays kill cancer cells).
Why is α dangerous if ingested?
High ionisation damages cells/DNA
Describe alpha radiation
Helium nucleus, +2 charge, paper-stopped.
Most ionizing, least penetrating
Describe beta radiation
High-speed electron, -1 charge, aluminum-stopped.
Moderate ionizing/penetrating, bends toward + plate.
Describe gamma radiation
EM wave, no charge, lead-stopped.
Least ionizing, most penetrating.
What is nuclear fission?
Splitting a heavy nucleus (e.g., uranium-235) into smaller nuclei + releases energy/neutrons
What type of neutron is most effective at initiating nuclear fission in Uranium-235?
A slow-moving neutron (also known as a thermal neutron).
What extremely high condition, besides density, is required for nuclear fusion to occur?
Extremely high temperatures (over 100 million degrees Celsius).
What is the fundamental difference in the nuclear reaction between nuclear fission and nuclear fusion?
Nuclear fission involves the splitting of a heavy atomic nucleus into smaller nuclei, while nuclear fusion involves the combining (fusing) of two light atomic nuclei into a heavier nucleus.
