1. CONSERVATION OF MASS-ENERGY

2. 6.4 ΔE = Δ c2m applies in all situations.
Simple calculations relating mass
difference to energy change.
Unified atomic mass unit, u.
Fission and fusion.

3. Building a helium nucleus

4. 2 protons and 2 neutrons 2 x Mp = 1.007825 = 2.015650
2 x Mn= =
expected mass of He nucleus =
Measured mass of He nucleus =

5. 2 protons and 2 neutrons 4.032980 - 4.002983 = 0.029997
The measured mass is les than the combined mass of the constituent nucleons

6. Argon 18 protons and 22 neutrons 18 x 1.007825 + 22 x 1.008665=
Measured value =
Again the measured mass is less than expected.

7. Binding Energy
When a nucleus is formed from its constituent nucleons energy is released.
This is equivalent to the energy that has to be supplied to retrieve the separate nucleons from the nucleus.
This energy is taken directly from the mass of the nucleus and is refereed to as binding energy.

8. Maximum stability
From about
M=50 to 100 8
Binding Energy per nucleon MeV 4 20 40 60
240
Atomic mass

9. fusion of lighter elements fission of heavier elements
It is energetically favourable to produce nuclei near the maximum. This can be brought about by:
fusion of lighter elements
fission of heavier elements
Binding Energy per nucleon MeV 8 4 20 40 60
Atomic Number
Atomic mass