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Chemistry Notes Part 1 Elements • Something that can not be broken down into a simpler form and maintain characteristic properties • Made up of only ONE type of atom • Russian Scientist • Invented the periodic table of elements Dimitri Mendeleev – Only 50 known elements • 1860s – Predicted new elements • Now: 118 known elements – #1-92 occur naturally – Only 88 are naturally found on earth • “Stuff” or “LEGOS®” of the universe Matter – Solid – Liquid – Gas – Plasma – BEC (Bose-Einstein Condensate) Atom Sub atomic particles • Basic unit of an element • Parts of an atom – Electrons: (-) • Orbits nucleus – Protons: (+) • In nucleus – Neutrons: (none) • In nucleus • ≥ 2 atoms bonded together Molecule • Ex: H2O • Ex: O2 • Ex: CO2 Element (Atomic) Number • Atomic # = # of Protons Electron number of an atom • Typically # of electrons = # of protons Atomic Mass • Mass of protons and neutrons Neutron # Atomic # Symbol Name Atomic Mass • Atomic mass minus atomic number= # of neutrons – EX: O (Oxygen) • Protons (+) = 8 • Electrons (-) = 8 • Neutrons (0) = 8 (16-8)=8 Rows • Periods – How many electron orbitals (shells) an atom has Columns • Groups of Families – Have similar characteristics and properties – Same # of valence electrons • Outer electrons of Valence Electrons an atom • Important for + are responsible for chemical reactions