Nuclear Physics

• Britain processes nuclear waste, a valuable economic business which has to be monitored very carefully.
• The disposal of waste has to be done with considerable care, and remains a truly controversial issue.
• Becquerel discovered that cathode ray tubes emitted X-rays that could expose photographic paper.
• Investigating a hunch that certain minerals emitted x-rays, Becquerel found that uranium compounds gave off particles he called “radiation.”
• α radiation is composed of +2 charged helium nuclei.
• β radiation consists of fast-moving electrons.
• γ radiation is high frequency light.
• Rutherford thought  particles would be the ideal particle to probe the atom.
• Rutherford developed his famous gold foil experiment to investigate the inner structure of the atom.
• This classic diffraction experiment was conducted in 1911 by Hans Geiger and Ernest Marsden at the suggestion of Ernest Rutherford.
• In the gold foil experiment,  particles were shot at a thin gold foil.
• A zinc sulfide detection screen surrounding the foil would fluorescence whenever radiation struck the screen.
• The gold foil had to be as thin as possible to avoid multiple scatterings.
• Geiger and Marsden expected to find that most of the alpha particles travel straight through the foil with little deviation, with the remainder being deviated by a percent or two.
• This thinking was based on the plum pudding model.
• The constant r0 is variable depending on the type of particle used.
• The relationship is always true, whatever the method used.
• Be careful not to confuse the nuclear radius with the atomic radius.
• The atomic radius is remarkably similar, whether the element is light or heavy.
• The nucleus occupies such a small fraction of the space in an atom that the atomic radius is similar for light and heavy elements.
• Use the nucleon number, not the proton number.
• E = mc2 is the famous equation known as the Atomic Mass unit.
• The atomic mass unit is defined as: Exactly 1/12th the mass of a carbon 12 atom.
• 1 atomic mass unit (u) = 1.661 ´ 10-27 kg.
• The table shows particle masses in atomic mass units.
• The atomic mass is the mass of an atom complete with its electrons; The nuclear mass is the mass of the nucleus alone.
• If we add together the mass of an electron and the mass of a single proton, we get the mass of a hydrogen atom.
• The atomic mass is 4.002603 u.
• All atoms are lighter than the sum of the masses of the protons, electrons, and neutrons; This is the mass defect, which is the difference between the total mass of the nucleons and the measured mass of the nucleus itself.
• To extract a proton or a neutron from the nucleus, we have to pull pretty hard; Then we find that it will regain its missing mass.
• The binding energy is defined as the energy released when a nucleus is assembled from its constituent nucleons; It is equal to the energy needed to tear the nucleus apart into its nucleons.
• The binding energy per nucleon is the average energy needed to remove each nucleon; The higher the binding energy per nucleon, the more stable is the nucleus.
• The binding energy per nucleon can be calculated from the binding energy in a nucleus and the number of nucleons; The binding energy per nucleon is a useful tool in understanding the stability of nuclides.
• Radioactive decay happens when an unstable nucleus emits radiation; It becomes more stable.
• What they found, to great surprise, was that most of the  particles passed right through the foil, implying the atom is mostly empty space.
• A few particles were wildly deflected, implying a large concentration of (+) charge in the center of the atom.
• Rutherford’s model of the atom included a dense, positively charged nucleus containing protons.
• Electrons were thought to orbit the nucleus like planets orbited the sun.
• If the new nucleus is unstable it will decay again, this is known as a decay chain.
• Some elements have a decay time of thousands of millions of years, while others can decay in microseconds.