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Intro to Chemistry Atomic Structure What is an Atom Smallest division of PURE MATTER matter that still retains physical and chemical properties of that Matter First Proposed by the Greeks 2400 years ago: name means indivisible Atomic Structure Atoms have 2 regions Nucleus- center of the atom contains protons and neutrons Electron Cloudempty space around atom which contains the electrons Nucleus: Center of the Atom Proton- + charged particle: Atomic Number Neutron- has NO charge Protons + Neutron= Atomic Mass of the element Electron Cloud Electron-smallest of the atomic particles; has no weight. Orbits around nucleus in electron cloud How the atom “works” Protons and Electrons “live” in the postively charged nucleus and make up the entire mass Electrons are negatively charged and occupy a large amount of space surrounding the nucleus Atom “basics” Number of Protons = Number of Electrons Neutrons have no charge so their number can change without changing the element Atomic Mass = # of Protons + # of Neutrons The Periodic Table Unit II—Part 4 The Father of the Periodic Table— Dimitri Mendeleev Mendeleev was the first scientist to notice the relationship between the elements Arranged his periodic table by atomic mass Said properties of unknown elements could be predicted by the properties of elements around the missing element Moseley later discovered that the periodic nature of the elements was associated with atomic number, not atomic mass The Periodic Table Column = Group or Family 18 columns on the Periodic Table Row = Period 7 rows on the Periodic Table What does the information in the box tell me? Atomic Number = # of protons (and electrons in its pure state) Atomic Mass = # of protons plus neutrons 1 H 1.008 Elemental Symbol Metals, Nonmetals, and Only Semi-metals Nonmetals are on the nonmetal on the metal side Metals are to the left of the stair- step Semi-metals, “metalloids,” touch the stair-step right of the stair-step The Groups of the Periodic Table Group 1 or (IA): The Alkali Metals Most reactive metals on the PT Rarely found free in nature Charge of 1—1 valence electron Group 2 (or IIA) : The Alkaline Earth Metals Still quite reactive Charge of 2—2 valence electrons T he Groups of the Periodic Table Groups 3-12: Transition Metals Found freely and in compounds in nature Charge is usually 2 but can vary—usually 2 valence electrons Group 13 (or IIIA): Boron Family Charge is 3—3 valence electrons The Groups of the Periodic Table Group 14 or (IVA): The Carbon Family Contains elements that can form unusual bonds (carbon and silicon) Charge is +4 or -4—contains 4 valence electrons Group 15 or (VA): The Nitrogen Family Charge is -3—contains 5 valence electrons The Groups of the Periodic Table Group 16 (or VIA): The Oxygen Family Group 17 (or VIIA): The Halogens Also known as the chalcogens Charge is -2—6 valence electrons Most reactive nonmetals charge is -1—7 valence electrons Group 18 (or VIIIA): The Noble Gases (The Inert Gases) Nonreactive Charge is 0—2 or 8 valence electrons Special Rows on the PT Lanthanides Actinides