10.1 Radioactivity Nuclear Decay Types of Nuclear Radiation Radioactivity happens when unstable atomic nucleus (called radioactive isotope or radioisotope) emits charged particles/E Nuclear decay is when atoms of one element change into atoms of another element Types of Nuclear Radiation Alpha Decay: U-238 emits + particle (2p+ and 2 neutrons/ looks like He nucleus) Beta Decay: Th-234 emits – particle (-1/ like e-) Gamma Decay: more penetrating and ray of energy emitted (no charge)
Effects of Nuclear Radiation Background radiation: radioisotopes occurring naturally in environment When exceeds background levels nuclear radiation ionizes atoms ALL damaging to tissues/deeper How we detect nuclear radiation Geiger counter: tool to measure amounts Film: badges: photographic film in paper to monitor radiation exposure
10.2 Rates of Nuclear Decay Half-life Time required for ½ sample of radioactive isotope to decay (breakdown) Decay rates are constant for radioisotope
Radioactive Dating: Age of an object (fossils) are determined Compares object’s C-14 levels with C-14 levels in atmosphere
10.3 Artificial Transmutation In Lab Nuclear decay is transmutation that happens naturally Artificially can hit nucleus with high E particles (p+, neutrons, or alpha particles) Transuranium Elements Atomic number above 92 (uranium) All radioactive and not normally found in nature Synthesized for lab, industrial, consumer use
Particle Accelerators Rutherford (Gold foil guy!) Used alpha particles Particle accelerators speed up particles close to speed of light (3.00x108 m/s) Quark: p+ and neutrons made of even smaller particles, among basic units of matter, 6 types exist
10.4 Fission and Fusion Nuclear Forces Fission Strong nuclear forces bind p+ and neutrons in nucleus Short distances, depend on # p+ Nucleus unstable (radioactive) when strong nuclear force can no longer overcome repulsive electric forces of p+ Fission German chemists: Otto Hahn and Fritz Strassman Splitting of atomic nucleus into 2 Were originally trying to make more massive elements, but made isotopes that were smaller!
Mass-Energy: E=mc2 Chain Reaction Nuclear E from Fission Fusion Neutron released during initial split trigger additional splitting Nuclear E from Fission Nuclear power plants generate 20% E in US + don’t make pollution, - make radioactive waste Chernobyl, Ukraine (’86) or 2 mile island, PA (’79) Fusion Nuclei combine to make larger nuclei