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Introduction to Physical Science Monday, Wednesday, Thursday Tom Burbine [email protected] Atoms • • • • • Atoms are made up of 3 types of particles Protons – positive charge (+1) Electrons – negative charge (-1) Neutrons – neutral charge (no charge) Protons and Neutrons are found in the nucleus Elements • Different elements have different numbers of protons • The properties of an atom are a function of the electrical charge of its nucleus Definitions • Atomic Number – Number of protons • Atomic Mass – Number of protons and neutrons • U235 – atomic mass 92- atomic number • Isotopes – Same number of protons but different numbers of neutrons • http://www.youtube.com/watch?v=GFIvXVMbII0 • http://www.chemicalelements.com/ • http://www.periodicvideos.com/ Periodic Table • A chart in which all known elements are listed in order of atomic number • http://theodoregray.com/periodictable/ • Period – Horizontal row • Across any period, the properties of elements change • Group – Vertical column • Down any group, the properties of elements are very similar Bohr’s Planetary Model • Electrons orbit the nucleus in specific energy levels • Level n=1 is closest to nucleus • Level n=2 is second closest Shell Model • Electrons behave as they are arranged in a series of concentric shells around the nucleus • Innermost shell can contain 2 electrons • The second and third shells can contain 8 electrons each • The fourth and fifth shells can contain 18 electrons each • Valence electrons are the electrons in the outermost shell • These electrons participate in chemical bonding Any Questions?