Phys - Nuclear Decay & Energy

Question 1

Relative Atomic Mass

Answer 1

System to measure mass where 1 = the mass of one nucleon

hydrogen has a Mr of 1

Question 2

Unified Atomic Mass Unit

Answer 2

u = 1.66x10^-27 kg = 1Da

Question 3

Mass Defect

Answer 3

Difference between predicted and actual mass of particles

Question 4

Binding Energy

Answer 4

E = [mass_defect]c^2 gives the energy needed to dissociate a nucleus into its constituent nucleons and energy released in reaction.

Question 5

Method For Analysing

Answer 5

1. Measure bg radiation with no absorbers
2. Measure source radiation
3. Measure with paper, add aluminium foil and measure again (and repeat with several meters of concrete in between source and detector)
4. If count drops with paper, alpha is present
   If count drops FURTHER with aluminium foil, beta is present.
   If count is above bg level, gamma is present (drops FURTHER with concrete, gamma is present).

Question 6

Becquerel

Answer 6

A = λN

Question 7

Uranium Chain Reaction

Answer 7

3 high-energy neutrons are released in the reaction, out of which one on average reacts with nearby Uranium atoms and causes fission, starting a domino effect.

Question 8

Binding Energy / Nucleon over Nucleon Number Graph

Answer 8

Elements can undergo exothermic fusion up to Ni-62 (Fe-56), combining elements of smaller atomic number to produce higher atomic number species and elements with nucleon numbers higher than 62 can undergo fission to reach a more stable state by breaking down by nuclear decay to produce a lower atomic number product.

They are exothermic if there is a reduction in mass from the reactants and product, meaning energy is released.

This is because Ni-62 is the most stable isotope due to its highest binding energy per nucleon.