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Question of the Day Rules • You must work alone • You may use your periodic table today • You have 6 minutes to complete the QOD Good luck!! Stoichiometry Question • Oxygen gas can be produced by decomposing potassium chlorate using the reaction below. If 138.6 g of KClO3 is heated and decomposes completely, what mass of oxygen gas is produced? KClO3 (s) --> KCl (s) + O2 (g) KClO3 (s) --> KCl (s) + O2 (g) 1. Balance your equation first. 2KClO3 (s) --> 2KCl (s) + 3O2 (g) 138.6 g KClO3 x 1 mol KClO3 x 122.55 g KClO3 3 mol O2 2 mol KClO3 x 32.0 g O2 1 mol O2 = 54.286 g O2 What are we doing Today? Nuclear Transformations Ch. 4 (EST) • Hand in Lab (Endo & Exo) • QOD • Nuclear Transformations (EST) • Practice Problems Nuclear Transformations p.124 - 131 Radioactivity • Radioactivity: Is a natural process in which an unstable atom spontaneously transforms into a more stable atom, or several more stable atoms, while releasing energy in the form of radiation (p.126) Nuclear Stability (p.125) • Nuclear Stability is a concept that helps to identify the stability of an isotope. Stability: you need to find the ratio of neutrons to protons. (Look at table 4.25 on page 125) • An unstable or radioactive substance may emit three types of radiation, referred to as ionizing radiation. Gamma rays • Is only made up of energy, not particles. They are neutral. • They can easily penetrate through materials. So you need a very dense material. (Lead) 87 38 Sr * 87 38 Sr + . The * in the reaction denotes an excited nuclear state. Alpha Particles. • Are positive particles • Large and Heavy, so can be stopped by a piece of paper. • The daughter nucleus has an atomic number 2 less and an atomic mass 4 less than the parent nucleus. • Example: 238 92 4 U 234 Th + 90 2 He . Beta Particles. • Are negative particles • Lighter then alpha particles and penetrate further • The daughter nucleus has an atomic number 1 more and an atomic mass the same as the parent nucleus. • Example: 14 6 C 147 N + e- . Later we will find there is something missing from this reaction. Here's a plot of the activity of a radionuclide. The initial activity was chosen to be 1000 for this plot. The half-life is 10 (in whatever time units we are using). All decay curves look like this; only the numbers on the axes will differ, depending on the radionuclide (which determines the half-life) and the amount of radioactive material (which determines the initial activity). Example: radon (nasty stuff) has a half-life of 3.8 days. If you start with 1 mg of radon, after 3.8 days you will have 0.5 mg of radon. Days 0 3.8 7.4 11.4 Radon Left (mg) 1 0.5 0.25 0.125 FUSION AND FISSION Fusion Reactions • 2 small nuclei release energy when they are fused together to form a single, larger nucleus • The process releases energy • Energy must be supplied to create bigger nuclei Nuclear Fission • Energy is released in a nuclear reactor as a result of nuclear fission • Fission is another word for splitting. • The nucleus of an atom of a fissionable substance splits into two smaller ‘fragment’ nuclei • This event can cause other fissionable nuclei to split, leading to a chain reaction of fission events • Two isotopes in common use as nuclear fuels are uranium-235 and plutonium-239 Chain • The additional neutrons released may also hit other uranium or plutonium nuclei and cause them to split – even more neutrons are then released, which in turn can split more nuclei. Called a chain reaction Chain Reaction Krypton n n n Uranium n Barium More decays Chain Reaction Chapter 4 EST Test • Chapter 4 EST Test on Wednesday, Dec 17 • Tutorial will be on Monday, Dec. 15 at 3:15pm That was the end of Chapter 4 (EST) Class Work 1) In your textbook p.134 Questions: 20, 21, 22, 23 2) In your textbook p.134 Questions: 24, 25, 26, 27, 28 25