Explain why a radioactive decay is a random process.
- There is equal probability of any nucleus decaying.
- It cannot be known which particular nucleus will decay next.
- It cannot be known at what time a particular nucleus will decay.
- The rate of decay is unaffected by surrounding conditions.
- It is only possible to estimate the proportion of nuclei decaying in the next time interval.
What is half life?
Half-life, T½ , of a radioactive isotope is the time taken for the mass of the isotope to decrease to half the initial mass.
What is activity?
- Activity, A, is the number of nuclei of the isotope which disintegrate each second, and is measured in becquerels (Bq).
- 1 becquerel = 1 disintegration per second
What is molar mass measured in?
Grams.
How many atoms does mass m of an element contain?
mNA/M
What is power of a radioactive source?
The product of activity and the energy of each particle.
As radioactive disintegration is a random process:
- ΔN is proportional to:
- N the number of nuclei remaining at time t
- The duration of the time interval Δt
Activty is the rate of change of:
The number of remaining nuclei with respect to time.
ΔN/Δt = -−λN
Solved differential equations for nuclear:
- N = Nₒe-λt
- A = Aₒe-λt
- C = Cₒe-λt
When graphed as natural logs.
y = c + mx is identical to ln N = ln Nₒ –λt
the gradient = −λ
intercept = lnN₀
What is the decay constant?
Decay constant, λ, is the probability of the an individual nucleus decaying per second. = ΔN/NΔt
T½ equation
ln2/λ
