An atom consists of a nucleus (containing protons and neutrons) surrounded by electrons in shells. Some atoms are radioactive because they have unstable nuclei with either too many protons or neutrons. These atoms undergo radioactive decay to achieve stability.
Click the button to simulate radioactive decay using virtual cubes. Green shows undecayed atoms, red shows decayed atoms.
| Type | Description | Penetrating Power | Shielding Required |
|---|---|---|---|
| Alpha (α) | Helium nucleus (2 protons + 2 neutrons) | Very low - stopped by paper | Paper or skin |
| Beta (β) | High-speed electron | Medium - stopped by aluminum | Thin metal sheet |
| Gamma (γ) | Electromagnetic radiation | Very high - passes through most materials | Thick lead or concrete |
Given the following data for Iodine-131, plot the activity vs. time and determine its half-life:
| Time (days) | 0 | 2 | 4 | 6 | 8 |
|---|---|---|---|---|---|
| Activity (Bq) | 100 | 91 | 83 | 76 | 69 |
Given the following data for Carbon-14, plot the activity vs. time and determine its half-life:
| Time (years) | 0 | 1000 | 2000 | 3000 | 4000 |
|---|---|---|---|---|---|
| Activity (relative) | 100 | 88.5 | 78.3 | 69.3 | 61.3 |
Iodine-131 Half-life: ~8 days
Carbon-14 Half-life: ~5,730 years
| Isotope | Applications | Problems/Risks |
|---|---|---|
| Americium-241 |
- Smoke detectors in homes - Industrial thickness gauges |
- Long half-life (432 years) - Toxic if ingested/inhaled - Proper disposal required |
| Cobalt-60 |
- Cancer treatment (radiotherapy) - Food sterilization - Industrial radiography |
- Strong gamma emitter - Requires heavy shielding - Potential environmental hazard |
| Iodine-131 |
- Thyroid cancer treatment - Diagnostic imaging |
- Can affect healthy thyroid tissue - Requires careful dosage control |
| Benefits | Drawbacks |
|---|---|
|
- Early detection of fires (smoke detectors) - Precise medical treatments - Non-destructive testing in industry - Extended food preservation - Accurate thickness measurements |
- Potential radiation exposure - Complex disposal procedures - High security requirements - Training needed for safe handling - Environmental concerns |
Americium-241 in smoke detectors represents a justified use of radioactive materials in homes for several compelling reasons:
While the disposal of smoke detectors requires special consideration, the protection they provide to human life and property makes them an essential safety device. The radiation risk from a properly manufactured and maintained smoke detector is negligible compared to natural background radiation.
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Release of radioactive materials including Iodine-131, Cesium-137, and Strontium-90
Immediate evacuation of nearby populations, acute radiation syndrome in workers
Contamination of soil and water, increased cancer risks, exclusion zone establishment
| Isotope | Half-life | Environmental Impact | Current Status (2024) |
|---|---|---|---|
| Iodine-131 | 8 days | Initial thyroid exposure risk | No longer present |
| Cesium-137 | 30 years | Soil contamination, food chain | ~50% of original remains |
| Strontium-90 | 29 years | Bone seeker, water contamination | ~50% of original remains |
| Plutonium-239 | 24,100 years | Long-term soil contamination | Nearly all still present |