Nuclear Chemistry Chapter 28

Nuclear force- what holds the atom together Two opposing forces in the nucleus: Electrostatic- proton vs proton repulsion Strong nuclear force-nucleons attracting eachother The strong nuclear force holds the protons and neutrons together, but acts over small distances

What is radioactivity Change in the atoms nucleus An atom can spontaneously emit particles An atom that emits radiation is radioactive Radiation is the particles that the atom emits Occurs in unstable isotopes

Radioactive decay The process in which the unstable isotope loses energy in the form of radiation Atoms emit radiation to become more stable.

Types of radioactive decay Alpha-composed of 2 protons and 2 neutrons, +2 charge, Stopped by paper, skin, etc. Beta-composed of a fast moving electron, with a -1 charge Stopped by aluminum foil Gamma- high energy particle, no mass, released with other radiation, never alone Stopped by Lead Alpha ()42He beta (–) 0–1e Gamma 

provide the entire energy requirements for 700 people for one year Mass and energy 30/09/99 Einstein suggested that mass and energy are related by E=mc2 (c = 3.0 x 108 m/s) E: energy, m: mass, c: speed of light Converting the mass of one penny could provide the entire energy requirements for 700 people for one year Power a space heater for 7000 years That’s about $3 million worth of electricity Because mass and energy are related the law of conservation of energy and law of conservation of mass can be combined into the Law of Conservation of Mass - Energy

Fission and Fusion 30/09/99 Two types of nuclear reactions are fusion and fission Fission is when a nucleus breaks apart Fission is used in nuclear power plants and powered the first atomic bomb (21 kilotons) Fusion involves adding nucleons to a nucleus Fusion powers stars and may also be used in thermonuclear bombs (60 megatons) Fusion requires that the nucleons be close enough so that the “strong force” can form

Fission Fission Fission chain (nuclear reactors)

FUSION

Half-Life The amount of time it takes for half the material to decay. After 1 half life half of the original material remains, after 2 half lives 25% of the original material remains, after 3 half lives 12.5% remains. Calculated as Amount remaining=(initial amount)(1/2)n n=number of half lives Amount remaining =(initial amount)(1/2)t/T t=elapsed time T=duration of half lives

Draw a table comparing, alpha, beta and gamma Name Symbol Composition Mass Charge What can shield us from it