Explain why a radioactive decay is a random process.

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- 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?

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- 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?

mN_{A}/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:

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- ΔN is proportional to:
- N the number of nuclei remaining at time t
- The duration of the time interval Δt

- 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:

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- N = Nₒe
^{-λt}
- A = Aₒe
^{-λt}
- C = Cₒe
^{-λt}

^{-λt}^{-λt}^{-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