2. Nuclear Reactions Atomic structure: Atomic structure: –Proton (+), Neutron (0), Electron (-) –Protons and Neutrons are found in the nucleus, where the majority of mass is found  Proton mass is small o- 1.67 x 10-27 kg  Neutron is 0.1% more massive  These are 2000 times as massive as electrons Atomic Number – number of protons Atomic Number – number of protons

3. Nuclear Reactions Isotopes – nuclei of the same element but with different number of neutrons Isotopes – nuclei of the same element but with different number of neutrons The number of protons + neutrons is known as the mass number The number of protons + neutrons is known as the mass number Isotopes are written with their individual mass number as superscript before the symbol – exa: 1 H - 1 proton, 0 neutrons Isotopes are written with their individual mass number as superscript before the symbol – exa: 1 H - 1 proton, 0 neutrons –Deuterium – 2 H – 1 proton, 1 neutron

4. Nuclear Reactions At high energies, nuclei can react to form new nuclei – there are two types of nuclear reactions At high energies, nuclei can react to form new nuclei – there are two types of nuclear reactions –Fission occurs when a heavy nucleus is split into two less massive nuclei –Fusion occurs when two light nuclei combine to produce a more massive nuclei  Two protons will combine to form 2 H – one proton changes into a neutron  H will then change into He

5. Nuclear Energy Matter is converted into energy during fission and fusion reactions Matter is converted into energy during fission and fusion reactions Einstein said that mass and energy are different forms of the same thing, hence: Einstein said that mass and energy are different forms of the same thing, hence: E = mc 2 Where E= energy, m= mass and c= speed of light Where E= energy, m= mass and c= speed of light

6. Nuclear Energy Energy is released if particles and nuclei that react are more massive than those produced Energy is released if particles and nuclei that react are more massive than those produced –For elements lighter than iron fusion produces energy and fission will require energy input –For elements more massive than iron, fission produces energy and fusion requires energy input Nuclear reactions produce much more energy than chemical reactions – heavy metal fission releases 100 milion times as much energy per atom Nuclear reactions produce much more energy than chemical reactions – heavy metal fission releases 100 milion times as much energy per atom

7. Radioactivity Decay of an isotope into other elements by emitting a particle that carries away mass and sometimes electrical charge. Decay of an isotope into other elements by emitting a particle that carries away mass and sometimes electrical charge. Half-life – the time it takes for half of the parent isotope to decay to the daughter isotope Half-life – the time it takes for half of the parent isotope to decay to the daughter isotope This predictable rate of decay makes it a perfect way to date rocks – called radiometric dating This predictable rate of decay makes it a perfect way to date rocks – called radiometric dating – 14 C is used to date formerly living things; half-life of 5730 years – 40 K decays to 40 Ar; half-life of 1.3 billion years

8. Internal Heat in Planets Radioactive heating – en ergy released by radioactive decay is the main source of heat in the interior of many planets and satellites. Radioactive heating – en ergy released by radioactive decay is the main source of heat in the interior of many planets and satellites. –Isotope must be abundant –Must release significant energy with decay –Must have a short half-life

9. Internal Heat in Planets Accretional Heating – heat generataed during the process of gradual accumulation from small pieces of matter Accretional Heating – heat generataed during the process of gradual accumulation from small pieces of matter Total accretional heating= sum of energy released by each piece of material as it is added Total accretional heating= sum of energy released by each piece of material as it is added

10. Flow of Heat Radiation – EM radiation carries energy from a hot region to a cool region Radiation – EM radiation carries energy from a hot region to a cool region Conduction – collisions among the particles of a gas, liquid or solid Conduction – collisions among the particles of a gas, liquid or solid Convection – energy carried by currents of a gas or liquid that rise from warm regions toward cool ones Convection – energy carried by currents of a gas or liquid that rise from warm regions toward cool ones