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Flashcards in Radioactivity Deck (12):
1

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.

2

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.

3

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 

4

What is molar mass measured in?

Grams.

5

How many atoms does mass m of an element contain?

mNA/M

6

What is power of a radioactive source?

The product of activity and the energy of each particle.

7

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

8

Activty is the rate of change of:

The number of remaining nuclei with respect to time.

ΔN/Δt = -−λN

9

Solved differential equations for nuclear:

  • N = Nₒe-λt
  • A = Aₒe-λt
  • C = Cₒe-λt

10

When graphed as natural logs.

y = c + mx is identical to ln N = ln Nₒ –λt

the gradient = −λ 

intercept = lnN₀

A image thumb
11

What is the decay constant?

Decay constant, λ, is the probability of the an individual nucleus decaying per second. = ΔN/NΔt

12

T½ equation

ln2/λ