NUCLEAR FORCES NOTES

Nuclear Forces Strong nuclear forces keep the nucleons together. These are powerful short-range force of attraction between the proton-proton, proton-neutron, and the neutron-neutron. This is distinct from the electrostatic force or gravitational force

Nuclear Mass Defect The difference between the mass of a nucleus and the sum of the masses of its constituent particles. The mass defect is converted into energy units by using Einstein’s equation, E= mc 2

nuclear binding energy The energy is usually referred to as the nuclear binding energy which is released when the nucleus is formed from its constituent particles

Comparison Lightest and heaviest elements have the smallest binding energies per nuclear particle. These are therefore less stable than the nuclei than the nuclei of elements having intermediate atomic weights.

Nuclear Stability (Refer to overhead of p. 803) In low atomic number elements, nuclei with greater number of neutrons than protons have lower binding energies and are less stable. The most stable have a 1:1 ratio of Neutron:Proton

Higher Atomic Number Stable nuclei have a neutron-proton ratio increasingly greater than 1:1

Odd-Even Stable – even Rarely stable -- odd

Radioactive Decay The emission of an alpha particle, a beta particle or gamma rays and the formation of slightly lighter and more stable nucleus

Nuclear Disintegration A nucleus is bombarded with alpha particles, protons, deuterons, neutrons or other particles. The unstable nucleus emits a proton or a neutron and becomes more stable

Fission The process in which a very heavy nucleus splits to form medium- weight nuclei

Fusion The process in which lightweight nuclei combine to form heavier, more stable nuclei

Properties of Radioacitive Nuclides The affect light –sensitive emulsion on a photographic film The produce an electric charge in the surrounding air(ionizing radiation) The produce fluorescence with certain other compounds Their radiations have special physiological effects The undergo radioactive decay

Half-life The length of time during which half of a given number of atoms of a radioactive nuclide decays

Nature of Radiation Alpha particles – slow, positive. Can burn flesh and ionize air easily Beta particles – fast, negative Gamma Rays- high-energy electromagnetic waves. Like visible light but much shorter wavelength and higher frequency

Shielding Ability Compare the materials needed to shield the alpha, beta and gamma Predictions??

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