Transcript Radiation
No Warmup Today TODAY we will review Atoms/Ions and learn about radioactivity Test on Friday will be about atoms, periodic table, ions, isotopes and electrons (valence and shells) and radioactivity Radiation What holds the nucleus together? Protons are pushing apart. Neutrons hold it together via nuclear force, or “strong” force. If nuclear force is greater than repulsion, nucleus stays together. But what if the forces aren’t strong enough to hold everything in place? Radiation click to watch : http://ed.ted.com/lessons/radioactivity-expect-the-unexpected-steve-weatherall Who? The 3 types of Radioactive Decay: •Alpha: Particle made of two protons, two neutrons. •“Heavy” particle •Positive charge •Can be stopped by a sheet of paper •Change Identity of parent when lost, loses 2 protons and 2 neutrons atomic # -2 atomic mass -4 4He+2 Who? The 3 types of Radioactive Decay: •Beta: an electron from nucleus – a neutron breaks apart •Have a negative charge and weigh less than a neutron or proton. •Will travel several meters in air, stopped by flesh or plastic. •Changes identity of atom – neutron turns into a proton: atomic # +1 0e-1 Three types of Radioactive Decay: •Gamma: An electromagnetic wave, NOT a particle •Short wavelengths and high frequency – HIGH ENERGY •DANGEROUS. Can do serious damage to living tissue due to their energy •Come from the excited nucleus AFTER it gives off alpha or beta particle •Can go through 2-3 cm of lead Why “decay?” When an atom gives off alpha or beta particles, it transforms into other elements. Another word for this transformation is decay. For example, Uranium238 will lose an alpha particle and turn into Thorium234 or: 238U -> 234Th + 4He 92 90 2+ Uranium loses two protons and its atomic number AND mass number changes. Thorium-234 keeps decaying…13 more reactions to become stable at Pb-206. …..it eventually turns into lead Two Types of Nuclear Reactions: Fission – one large atom splits when a neutron hits a nucleus and splits it apart, releasing energy THINK DIVISION Found in two places: http://www.youtube.com/watch?v=11e8XyUBqRQ UNCONTROLLED FISSION Nuclear Energy, made simple CONTROLLED FISSION Two Types of Nuclear Reactions: Fusion – Two small nuclei fuse together THINK FUSE TOGETHER While we’re talking radiation… Half-life: The period of time for a substance undergoing decay to decrease by half. For example, Uranium-238’s half-life is 4.46 billion years. Slow decay by emitting an alpha particle. If I had 1,000 g of U-238, in 4.46 billion years, I would have 500g of U-238. Carbon-14’s half-life is 5730 years. Useful for dating organic items of age since it’s in all living tissue. In other words… Parent Element: The original one that is going through radioactive decay unstable Daughter Element: The element that the parent changed into (replaces the parent) more stable Let’s try it… say, a half life of 30 years and 500 g. How much left in 90 years? Half life = 30 years, how many half lives in 90? 90/3 = 3 1st Half Life- after 30 years, we would have: 250 g 2nd half life-after 60 years would be ½ of 250g: 125g 3rd half life- after 90 years would be ½ of 125: 62.5g Fukushima, over a year ago Nuclear Power Benefits? Are there greenhouse gasses? Is it efficient? Is there waste? Risks? Coal vs. Natural Gas vs. Oil vs. Nuclear