Nuclear Chemistry Nucleus is held together by “strong” or “nuclear” forces. –Strongest forces in the universe –Between like charges –The closer the charged particles, the stronger the force Too many neutrons can get in the way of this force and make the nucleus unstable. “Neutron-Heavy” isotopes stabilize in two ways: –Emitting small amounts of radioactivity –Flying apart with great amounts of energy

Spontaneous Radioactive Decay Nucleus spontaneously changes structure to reduce the number of neutrons and become more stable. –Alpha particle emission –Beta particle emission –Gamma ray emission

Alpha Decay Atomic number decreases by 2 Element changes - transmutation

Beta Decay - Atomic number INCREASES by 1 Element changes - transmutation

Gamma Radiation Emission of gamma rays (γ) Very high energy light waves with high frequency Non-particulate in nature Mass is lost!!!

Half-Life Time required for half an amount of isotope to decay Varies from fractions of a second to billions of years Formula: Practice: If you have 10 Kg of radioactive Barium and the half-life is 13 days, how much barium will be left after 100 days?

Applications of Radioactivity Smoke detectors –Use americium Medicine –Imaging and analysis –Cancer treatment Determining the age of the earth –U-238 present in rocks slowly decays to Pb-206 –The age of the earth is: 4.5 billion years!!!

NUCLEAR FISSION Nucleus of a radioactive element splits by bombardment from an external source Simultaneous release of large amounts of energy, in the form of heat, light and sound – Exothermic Process!!

Nuclear Fission Neutron induced to U 235 The sum of the masses of the resulting nuclei is about 0.1% less than the original mass The “missing mass” is converted to energy according to E=mc 2

Chain Reactions Three neutrons are released and may: Cause another fission by colliding with a U 235 nucleus. If enough neutrons are present a chain reaction will occur. Called the Critical Mass Each split released a large amount of ENERGY! Be absorbed in other material Get lost in the system

Destructive Fission Reactions Chernobyl Atomic Bombs dropped on Japan

Nuclear Fission Power Similar to Coal power Heat is generated by a fission reaction rather than from the burning of coal Benefits: cheaper after setup, uses very little fuel Drawbacks: can be dangerous if reaction is not controlled, creates radioactive waste

Nuclear Reactors Control rods absorb neutrons to control the rate of reaction. Nuclear subs use this technology so they do not have to transport gasoline or coal.

Nuclear Fusion Multiple nuclei join together to form a heavier nucleus. Releases of large amounts of energy. The sun converts hydrogen to helium in a fusion reaction. This is the source of most of our ENERGY

Fusion Power Benefits: uses plentiful hydrogen, creates very large amounts of energy Drawbacks: –requires massive amounts of heat to start the reaction –Too little mass to create a sustained reaction Uses of fusion already: –Sun –Hydrogen bomb never used in wartime 10X power of atomic bomb Initial heat produced by a small atomic bomb inside Hydrogen Bomb Video

Innovations in Nuclear Chemistry Particle accelerators – “atom smashers” Large Hadron Colider – CERN –Opened Sept. 09, 2008