Nuclear Chemistry Chapter 25. What do you think of when you hear Nuclear Chemistry?
Post on 31-Mar-2015
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Nuclear Chemistry Chapter 25 Slide 2 What do you think of when you hear Nuclear Chemistry? Slide 3 History Henri Becquerel (1852-1908) Originally thought sunlight caused uranium to radiate Discovered the spontaneous radiation while waiting for a sunny day to test his theory Marie Curie (1867-1934) and her husband Pierre Curie (1859-1906) Worked w/ Becquerel Eventually showed that the rays were from uranium atoms Came up with the term radioactivity to describe Slide 4 Why Radioactive? Some isotopes are stable and others are not. Nucleus is protons and neutrons Protons are positive so they repel Neutrons are only stable when near a proton Some have: Too many protons Too many neutrons Just plain too many So they fall apart Slide 5 First 3 kinds of radiation found Slide 6 Slide 7 Summary of Radiation ALPHA Positive matter Exactly like a Helium nucleus BETA Negative matter Exactly like an electron GAMMA High energy wave NOT matter so no charge Slide 8 Types of Radiation Alpha Radiation- when a helium nuclei has been emitted from a radioactive source. Slide 9 Types of Radiation Beta Radiation An electron resulting from the breaking apart of a neutron in an atom. Slide 10 Types of Radiation Gamma Radiation a high-energy photon emitted by a radioisotope. (electromagnetic radiation) Extremely Dangerous! Slide 11 Type of Radiation SymbolMass Nuclear Charge Particle Alpha 4 amu 2 + Beta 1 - Gamma 0 0 Slide 12 How can we use what we know? Look for patterns Try to explain the patterns Test your ideas with known things Use the pattern to figure out unknown things Adjust as necessary! Slide 13 The blue ones have at least one stable isotope. Others do not! Slide 14 http://catalog.flatworldknowledge.com Slide 15 How does this help? Chart helps predict type of decay Too many neutrons? Emit a beta particle to change a neutron to a proton and move closer to the band of stability Just too big? Emit an alpha particle to reduce size of nucleus There are many types of decay, but chart helps give us targets when trying to manipulate elements to do what we want Slide 16 Writing and Balancing Nuclear Equations Slide 17 Slide 18 Practice Slide 19 Half -Life Half-Life is the time required for half of the atoms in a radioactive sample to decay Number of half-lives Elapsed timeAmount of strontium-90 present 00 y10.0g 129 y5.00g 258 y2.50g 387 y1.25g 4116 y0.625g Slide 20 Half-Life Practice Bandages can be sterilized by exposure to gamma radiation from colbalt-60, which has a half-life of 5.27 years. How much of a 10.0 mg sample of cobalt-60 is left after one half-life? Two half-lives? Three half- lives? How many years is 3 half-lives? 5.00mg; 2.50mg; 1.25mg; 15.81y