Nuclear Chemistry - Seneca High School Homepage：核化学塞内卡中学主页.pptVIP

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Nuclear Chemistry - Seneca High School Homepage：核化学塞内卡中学主页.ppt

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Nuclear Chemistry - Seneca High School Homepage：核化学塞内卡中学主页

Nuclear Chemistry Chapter 25 What do you think of when you hear Nuclear Chemistry? 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 Radiation – penetrating rays and particles emitted by a radioactive source. Radiation An unstable nucleus releases energy by emitting radiation during the process of radioactive decay. What is an unstable nucleus? Stability depends of the neutron to proton ratio. Atoms with low atomic numbers (1-20) have a 1:1 ratio. Above 20, stable nuclei have a 1.5:1 ratio. Alpha Decay - Alpha Decay, Alpha Particles, Radioactivity - PhET Types of Radiation Alpha Radiation- when a helium nuclei has been emitted from a radioactive source. Types of Radiation Beta Radiation – An electron resulting from the breaking apart of a neutron in an atom. Types of Radiation Gamma Radiation – a high-energy photon emitted by a radioisotope. (electromagnetic radiation) Extremely Dangerous! 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 Types of Decay neutron to proton ratio determines the type of decay Four Types of Decay Beta Decay Electron Capture Positron Emission Alpha Decay Beta Decay Too Many Neutrons! Beta Decay – neutron turned into a proton and electron 1 0 n 1 1 H + 0 -1 e Example: 14 6 C 14 7 N + 0 -1 e Electron Capture Too few neutrons! Electron Capture – convert proton to neutron; an e- is captured. Example: 37 18 Ar + 0 -1 e 37 17 Cl Positron Emission Positron – particle with the mass of an electron but a positive charge A proton changes to a neutron. Example: 8 5 B 8 4 Be + 0 +1 e Alpha Decay Too many neutrons an