7b-Radioactivity Flashcards
What is the structure of an atom?
A: An atom consists of:
Protons (positively charged, in the nucleus)
Neutrons (neutral, in the nucleus)
Electrons (negatively charged, orbiting the nucleus in shells)
What do atomic symbols represent?
A: An atomic symbol such as means:
Mass number (A) = 14 (Total protons + neutrons)
Atomic number (Z) = 6 (Number of protons)
Atomic (proton) number (Z):
Number of protons in the nucleus.
.
Mass (nucleon) number (A):
Total number of protons + neutrons.
Isotopes:
Atoms of the same element with the same number of protons but different numbers of neutrons
Alpha
Alpha (α) particles:
2 protons and 2 neutrons (Helium nucleus)
Strongly ionising, low penetration (stopped by paper)
Beta
Beta (β⁻) particles:
Fast-moving electron
Moderately ionising, moderate penetration (stopped by aluminium)
Gamma
Gamma (γ) rays:
Electromagnetic wave
Weakly ionising, high penetration (stopped by thick lead)
Practical: Investigating Radiation Penetration
Q: How can you test radiation penetration?A:
Method: Use a Geiger-Müller (GM) tube and measure count rate with different materials.
Observation:
Paper blocks alpha.
Aluminium blocks beta.
Lead blocks gamma.
Q: How does emission affect atomic and mass numbers?
Alpha
Alpha decay: Decreases mass number by 4, atomic number by 2.
Q: How does emission affect atomic and mass numbers?A:
Beta
Beta decay: Increases atomic number by 1 (neutron changes to proton).
Q: How does emission affect atomic and mass numbers?A:
Gamma
Gamma decay: No change in numbers, only energy release.
Q: How does emission affect atomic and mass numbers?A:
Neutron
Neutron emission: Decreases mass number by 1, atomic number remains the same.
How do you balance nuclear equations?
A: Total mass and charge must be conserved.
^226 Ra 88 -> ^222 Rn 86 + ^4He2
Example:
(Radium undergoes alpha decay to form Radon and an Alpha particle)
Q: How can ionising radiation be detected?A:
Photographic film (darkens when exposed to radiation).
Geiger-Müller (GM) tube (detects and counts radiation pulses).
Q: What are sources of background radiation?A:
Natural sources: Cosmic rays, radon gas, rocks.
Artificial sources: Medical procedures (X-rays), nuclear power.
Q: How does radioactive activity change over time?A:
It decreases over time, measured in becquerels (Bq).
Q: What is half-life?A:
The time it takes for half of the radioactive nuclei in a sample to decay.
Q: What are some applications of radioactivity?A:
Industry: Checking for leaks in pipes (tracer isotopes), thickness control in manufacturing.
Medicine: Cancer treatment (radiotherapy), sterilisation of medical instruments.
Q: What is the difference between contamination and irradiation?A:
Contamination: Radioactive material is inside or on an object/person, making it a long-term hazard.
Irradiation: Exposure to radiation only, stops when source is removed.
Q: How can exposure to radiation be reduced?A:
Shielding (lead, concrete) to block radiation.
Minimising exposure time.
Increasing distance from the source.
Q: What are the dangers of ionising radiation?A:
Causes mutations in living organisms (DNA damage → cancer risk).
Damages cells and tissues (burns, sickness from exposure).
Radioactive waste disposal issues (long half-lives → environmental hazard).
Q: How can the risks of radioactive waste be managed?A:
Storage in lead-lined containers.
Burying deep underground in stable locations.
Dilution and controlled release.
