Nuclear decay

Question 1

What is an isotope

Answer 1

An element with the same number of protons but different number of neutrons

Question 2

What is radioactive decay?

Answer 2

The process by which an unstable nucleus becomes a more stable nucleus by decaying into a daughter nucleus while emitting particles; alpha, beta or gamma

Question 3

What is alpha radiation

Answer 3

A nucleus decays into a smaller, stable nucleus, releasing a fast moving helium nuclei

Question 4

What is beta radiation

Answer 4

A neutron in an unstable nucleus decays into a proton and releases a fast moving electron

Question 5

What is gamma radiation

Answer 5

An unstable nucleus releases some energy in the form of a
gamma photon. This often accompanies one of the other types
of decay

Question 6

During decay do the mass numbers remain constant?

Answer 6

Yes

Question 7

During decay does the sum of proton numbers change?

Answer 7

No-the sum remains constant

Question 8

What kind of radiation is usually produced during nuclear decay

Answer 8

alpha and gamma or beta and gamma

Question 9

What is activity and what is it measured in?

Answer 9

The rate of decay of a sample of radioactive nuclei.
It is measured in Becquerel (Bq)

Question 10

How can you distinguish between each type of radiation

Answer 10

Penetrating power or use of electric fields

Question 11

How would you set up the penetrating power experiment?

Answer 11

A sealed radioactive source, placed next to a geiger counter.

Question 12

Explain how you would get results for a penetrating power experiment which would determine which radiation is present

Answer 12

1. Take readings of background radiation by using the geiger counter
2. Place a sheet of paper between the source and the geiger counter. If there is a significant drop in count rate then there is alpha radiation present
3. Then place a sheet of aluminium in between the source and the counter. If there is a further significant drop there must be beta radiation present
4. Then place a lead block in between the source and the counter. If there is another significant drop, gamma is present

Note: not all radiation is absorbed. there may be a count rate after all absorbers have been used (minusing the background radiation)

Question 13

What must we be weary of when discussing results of the penetrating power experiment

Answer 13

1.Paper will absorb some beta radiation
2. aluminium will absorb some gamma
3. We must take background radiation into account unless it’s negligible compared to the results
4. There may be random errors

Question 14

Which radiation is more ionizing, a radiation with higher penetrating properties or lower penetrating properties?

Answer 14

The more ionizing the radiation, the lower the penetrating properties

Question 15

What radiation is the most ionizing and why?

Answer 15

alpha, higher charge, larger mass and moves slower

Question 16

How would you set up the electric fields experiment to determine what radiation is present in a radioactive source

Answer 16

a radioactive source placed in a shielded container

Question 17

electric fields need to continue

Question 18

What is half life

Answer 18

Half life is the time taken for the number of radioactive nuclei to reduce to half the initial value

Question 19

What is the equation to determine the number of radioactive nuclei

Answer 19

N=N0/2^x
N=number of nuclei
N0=number of unstable nuclei at time t=0
x=number of half lives

Question 20

What is the equation to determine the rate of decay

Answer 20

A=A0/2^x
A=rate of decay
A0=rate of decay at t=0

Question 21

Why is decay a constant (λ)?

Answer 21

Because A∝N
so A=λN

Question 22

Derive λ=ln2/Tx1/2

Answer 22

Check notes for answer