8.1.3 Radioactive Decay Flashcards
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| 16302145409 | What is radioactive decay? | The process of unstable atoms changing into smaller more stable atoms Random process - cannot predict which atoms will decay |  | 0 |
| 16302162031 | What is the decay constant? | The probability of a specific nucleus decaying per unit time |  | 1 |
| 16302194392 | What are the units of the decay constant? | s⁻¹ |  | 2 |
| 16302258601 | What is the equation for decay constant? | λ = -ΔN/ΔtN Negative as ΔN is always a decrease |  | 3 |
| 16302300139 | What is the exponential equation for the number of unstable nuclei remaining? | N = N₀ e⁻^λt Where N - Number of unstable nuclei remaining N₀ - Initial number of nuclei λ - Decay constant t - time for decay |  | 4 |
| 16302359090 | What is the activity of a radioactive sample? | The number of nuclei that decay per second |  | 5 |
| 16302367876 | What are the units for activity? | Bq |  | 6 |
| 16302389667 | What is the equation for activity? | A = Nλ Where A - Activity in Bq N - Number of unstable nuclei λ - Decay constant in s⁻¹ |  | 7 |
| 16302448454 | What is the graph for number of unstable nuclei remaining N against time? |  | 8 | |
| 16302463521 | What is the logarithmic equation for the number of unstable nuclei remaining? | lnN = lnN₀ - λt On a graph - lnN - y-axis lnN₀ - y-intercept λ - gradient t - time | | 9 |
| 16302532578 | What is half life? | The time taken for the number of nuclei to halve |  | 10 |
| 16302553897 | What is the equation for half life? | T 1/2 = ln2 / λ | | 11 |
| 16302569184 | How can you calculate half life graphically? |  | 12 | |
| 16302607619 | What is the number of atoms in a sample equal to? | N = n Na Where N - Number of atoms n - Number of moles Na - Avogadro's constant |  | 13 |
| 16302668759 | What is the exponential equation for the activity? | A = A₀ e^-λt | | 14 |
| 16302709159 | What is radioactive dating? | - Carbon -14 is used in radioactive dating - Most organic material will contain this isotope - Has a very large half life of 5730 years |  | 15 |
| 16302747238 | What are the problems with radioactive dating? | - For man-made objects only the age of the material can be dated - May be contaminated with other sources - High background count - Small sample, statistically insignificant | | 16 |
| 16302820563 | What is the use of Tc-99 in medical diagnosis? | - Used as a medical tracer to show the tissue or organ function, pure gamma emitter - Radiation emitted is recorded and an image of inside the patient is produced - Half life of 6 hours (short enough to limit exposure), can be prepared on site |  | 17 |
| 16303202199 | How can we store nuclear waste? | - With extreme long half lives they can be stored in steel casks underground |  | 18 |