Alpha Radiation (α)  A helium nucleus of 2 protons and 2 neutrons, mass=4, charge= +2  4 2 He  Low penetration stopped by a few cm of air or thin sheet of paper  Reduces the atomic mass number by 4; reduces the atomic number by 2

Beta Radiation (β)  High kinetic energy electrons, mass=1/1850 of alpha, charge= -1  0 -1 e  Moderate penetration, most stopped by a few mm of metals like aluminum  Is the result of neutron decay and will increase the atomic number by 1 but will not change the mass number

Gamma Radiation (γ)  Very high frequency electromagnetic radiation, mass=0, charge=0  0 0 γ  Very highly penetrating, most stopped by a think layer of steel or concrete, but even a few cm of dense lead doesn’t stop all of it  Is electromagnetic radiation released from an excited nucleus. The atomic number and mass number do not change.

The Nucleus  Positively charged  Contains most of the atom’s mass (protons and neutrons) at the center of the atom.  Protons and neutrons = nucleons  The more tightly the nucleons are held together, the more stable the nucleus of the atom.  2 Forces are acting within the nucleus:  Electrostatic forces (repulsion between protons)  Strong nuclear forces (short range attractions between protons and neutrons)

Nuclear Stability  As the number of protons increases, the repulsive electrostatic force increases requiring more neutrons to stabilize the nucleus.  Unstable nuclei undergo spontaneous changes to obtain stability…resulting in nuclear reactions.

Fission & Fusion  The energies in these reactions exceed the energies in usual chemical reactions (nuclear energy releases vastly more energy).

Fission- heavier nuclei are split to form lighter nuclei

Fusion- lighter nuclei combine to form more stable heavier nuclei

Nuclear Reactions Fusion  Energy released by the SUN results from nuclear fusion.  Remember sUn has a U and fUsion has a U.  Release more energy than fission reactions  Only occur at very high temperatures (over 40,000,000 degrees Celsius)  Reaching these temperatures and controlling these reactions is very difficult – so we don’t have fusion power plants  H-bomb (developed but has never been used in war) Fission  Can occur spontaneously or when isotopes (Uranium-235 & Plutonium-239) are bombarded with a neutron  Causes a chain reaction-some of the neutrons produced react with other fissionable atoms, producing more neutrons which react with still more fissionable atoms  Atomic bombs-start uncontrolled nuclear chain reactions (bombs dropped on Hiroshima & Nagasaki)  Can be controlled to release energy more slowly-nuclear power plants that generate electricity

Exit Ticket  What does your graph tell you about the definition of half life? Explain your reasoning.  Describe in one sentence what you learned from the skittles activity.  Compare and contrast fusion and fission.