Lecture 3

Question 1

What are the 4 decay series

Answer 1

1. Thorium 4n
2. Neptunium 4n+1
3. Uranium 4n+2
4. Actinium 4n+3

Question 2

Why are certain elements the names of the decay series

Answer 2

1. Occur naturally
2. Parent members of their respective series
3. have longest half life periods

Question 3

How does the nuclear decay series work

Answer 3

1. Decay by a series of alpha and beta emissions
2. produce radioactive which are successively more stable until finally a stable isotope is reached

Question 4

What does the Thorium series end in

Answer 4

1. 208,82Pb

Question 5

What does the Neptunium series end in

Answer 5

1. 209,93Bi

Question 6

What does the Uranium series end in

Answer 6

1. 206,82Pb

Question 7

What does the Actinium series end in

Answer 7

1. 207,82Pb

Question 8

What must all members of a decay series differ by

Answer 8

1. A multiple of 4

Question 9

What happens in radioactive equilibrium

Answer 9

1. THe ratio of nucleo occuring is equal to the ratio of their half lives

Question 10

What does the thorium series start with

Answer 10

1. 232,90Th

Question 11

What does the Neptunium series start with

Answer 11

1. 241,94 Pu

Question 12

What does the Uranium series start with

Answer 12

1. 238,92U

Question 13

What does the Actinium series start with

Answer 13

1. 239,92U

Question 14

What is half life period

Answer 14

1. The time taken for half the radioactive nuclei in a sample to decay

Question 15

What type of reaction is radioactive decay in terms of kinetics

Answer 15

1. First order
2. Doesn’t depend on size of sample

Question 16

What is the differential equation for rate of decay

Answer 16

1. A=dN(t)/dt=gammaN(t)
2. A = activity- number of disintegrations per unit time of the radioactive sample
3. N= number of nuclei
4. Gamma= decay constant- units of time^-1

Question 17

What is the integral equation for rate decay

Answer 17

1. N(t) = N0e^-gamma.t
2. A(t)= A0e^-gamma.t
3. Anything proportional to N can be substituted in
4. N0 is number of nuclei at time 0
5. N is number remaining at time t

Question 18

What does half life allow

Answer 18

1. Each radioactive nuclide has a characteristic, constant half life (t1/2), the time required for half of the atoms in a sample to decay
2. An isotopes half life allows us to determine how long a sample of a useful isotope will be available
3. And how long a sample of an undesirable or dangerous isotope must be stored before it decays to a low enough radiation level that is no longer a problem

Question 19

What is equation for half life

Answer 19

1. t1/2= ln(2)/ gamma
2. p29 has all equations to remember

Question 20

What are the units for measuring radioactivity

Answer 20

1. Becquerel- Bq- SI unit of activity corresponding to one disintegration per second
2. Curie- activity of 1g of pure 226Ra, equivalent to 3.7*10^10Bq