1
Its not Nuclear Science or is it?

• Chemical changes involve the transfer of
  electrons. In chemical reactions atoms are
  re-arranged to form new products.
• Nuclear reactions involve a change in the nucleus
  of the atom.
• A change in protons or neutrons will create a new
  species, either an isotope or a new element.

2
Notation

• Mass number is the total number of protons and
  neutrons.
• Atomic number is the total number of protons
• Nuclear changes are balanced using conservation
  of mass number and atomic number

3
Use the force Luke

• What holds the net positive nucleus together?
• The strong nuclear force overcomes the
  electrostatic repulsion of the protons and binds
  the nucleus together.

4
Nuclear Binding Energy

• Energy is required to bind the nucleus together.
• This energy comes from the difference in mass
  between the atom and its parts.
• Mass defect is the difference in mass between the
  number of neutrons and protons and the mass of
  the nucleus together.
• E mc2 gives the amount of energy

5
Mass Defect

• Proton Mass 1.007825
• Neutron mass 1.008665
• Mass of O-16 is 15.994915
• Difference in mass between 8 protons and 8
  neutrons is the mass defect (.137005).
• It is converted into energy to hold the nucleus
  together using emc2.

6
Binding Energy per Nucleon
7
Valley of Stability indicates stable nuclei. The
ratio of neutrons to protons increases for stable
nuclei as mass number increases.
8
Nuclear Decay

• Nuclear processes occur because of an instability
  between the number of protons and neutrons in the
  nucleus.
• During nuclear reactions, a particle from the
  nucleus is given off which results in
• Change of proton to a neutron
• Change of neutron to a proton
• Release of energy and radiation

9
Nuclear Decay Particles

• Beta particle ß-
• Electron emitted from the nucleus
• Changes a neutron to a proton
• Positron emission ß
• Positive electron emitted from the nucleus
• Changes a proton to a neutron
• Alpha particle
• A particle with 2 protons and 2 neutrons
• Gamma particle
• A high energy particle of radiation, no mass

10
Radioactive equations
11
Atomic Fission

• Nuclear fission occurs when a heavy nucleus such
  as U-235 splits into two smaller nuclei.
• The total rest mass of the products is less than
  the original rest mass.
• The mass difference is converted to the energy
  released using emc2
• This process occurs naturally at a slow rate, but
  can be accelerated by neutron bombardment in the
  laboratory.

12
Neutron Bombardment of U-235

• U-235 absorbs a slow moving neutron.
• U-236 is unstable and lasts for only 10-12 s.
• The U-236 nucleus splits into two fragments and
  emits several neutrons.

13
Nuclear Fusion

• Lighter nuclei undergo a process called nuclear
  fusion
• Fusion takes a great amount of energy to be
  initiated in order to overcome the proton-proton
  barrier between nuclei.
• However, a greater amount of energy is released
  in the process.
• Stars produce their energy through the fusion
  process.

14
Fusion Process

• Hydrogen is fused together forming deuterium.
• He-3 is formed from hydrogen isotopes.
• He-4 is formed through 2 different processes.
• The energy is produced though the gamma,
  neutrino, and positron emission.