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1、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 P
2、ierre 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 t
3、he 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
4、 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) Extreme
5、ly 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 Posi
6、tron Emission Alpha Decay,Beta Decay,Too Many Neutrons! Beta Decay neutron turned into a proton and electron,Example:,Electron Capture,Too few neutrons! Electron Capture convert proton to neutron; an e- is captured.,Example:,Positron Emission,Positron particle with the mass of an electron but a posi
7、tive charge A proton changes to a neutron.,Example:,Alpha Decay,Too many neutrons and too many protons! Most common in atoms with an atomic number greater than 83. Alpha Emission release of an alpha particle.,Example:,The blue ones have at least one stable isotope. Others do not!,Half-Life,Half-life: is the time required for one half of the nuclei of a radio isotope sample to decay to stable products.,