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7.1 Atomic Theory and Radioactive Decay Natural background radiation exists all around us. ____________________ is the release of high energy particles or waves. - When atoms lose high energy particles and waves, ________________ can be formed. – Radiation is useful (medical scans & cancer treatment) but it damages DNA in cells. The Electromagnetic Spectrum Isotopes are different atoms of the same element, with a different number of __________ in the nucleus. – changing the # of ____________ changes the _____________ number Remember: mass # = ________________________________ – isotopes still have the same __________________________________ Atomic Mass (the decimal #’s) Atomic mass = ___________________________________________________. Representing Isotopes Isotopes are written using standard atomic notation. – Chemical symbol + atomic number + mass number. – Potassium has three isotopes, Radioactive Decay Can result in new __________ forming. – Radioactivity results from having an _____________ ____________. – Radioactive decay = when nuclei break apart + release ___________ from the nucleus as __________________. Radioactive decay continues until a _________ element forms. An element may have only certain isotopes that are radioactive called ____________________ Uranium goes through many decay steps before it becomes stable. Rutherford identified three types of radiation using an electric field. – Positive _____________________ were attracted to the negative plate. – Negative ____________________ were attracted to the positive plate. – Neutral _____________________ did not move towards any plate. A) Alpha Radiation: is a stream of alpha particles, (shown as ) – _______________________ – the most massive of the 3 types and are the equal to a Helium nucleus. – Alpha particles are represented by the symbols: 2 protons and 2 neutrons make a mass number of 4 it has a charge of 2+ because of the protons Alpha particles are ____________ and penetrate materials much less than the other forms of radiation. A sheet of paper will stop an alpha particle. The release of alpha particles is called _____________ _____________. Example: the alpha decay of Radium – 226 B) Beta Radiation: A Beta particle, ________ is a _________ ____________ _______________. – _____________ charged, and are _________ massive than alpha particles. – Beta particles are represented by the symbols : electrons are very tiny, so beta particles are assigned a mass of __. one electron gives a beta particle has a charge of ___________. Beta decay occurs when a neutron changes into a _________ + an ___________. The proton stays in the ___________, and the electron is _____________. Example: The beta decay of iodine - 131 It takes a thin sheet of aluminum foil to stop a beta particle. C) Gamma Radiation: Gamma radiation, ___, is a ray of _________ energy, short-wavelength radiation. – has ____ charge and _____ mass. – is the _____________ energy form of electromagnetic radiation. – It takes thick blocks of lead or concrete to stop gamma rays. – Gamma decay results from ____________ being released from a high-energy ________________. Often, other kinds of radioactive decay will also release gamma radiation. – Uranium-238 decays into an alpha particle and also releases gamma rays. Nuclear Equations: are written like chemical equations, but represent ___________ in the ___________ of atoms. – Chemical equations represent changes in the position of atoms, not changes to the atoms themselves. Remember: – The sum of the ________ ___________ on each side of the equation should equal. – The sum of the __________ on each side of the equation should equal.