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Chemistry Overview Elements • Element: pure substance that can’t be broken down into simpler substances • Element Symbols – 1-3 letters – Begin with 1 capital letter – Some based on Latin names • Ex/ gold = Au for Aurum iron = Fe for Ferros Structure Atoms • Smallest particle identified as an element • Dif. atomic structures = different elements • Atom is made of 3 particles – Proton – Neutron – Electron Atomic Structure 1. Nucleus – responsible for element’s ID • • Proton – positive charged particle Neutron - neutral charged particle w/ = mass as proton 2. Electron cloud – surrounds the nucleus • • Electron – negatively charged Revolves around nucleus More Atomic Structure • Electrons arranged into energy levels (layers) • Valence electrons – electrons on outer energy level (layer) – Responsible for bonding between atoms – Responsible for the reactivity of elements An Atom Elements on the Periodic Table Calculating Atomic Structure Atomic # = # of protons in nucleus # of protons = # of electrons # Neutrons = Atomic mass - # protons Combining Elements • Compounds – 2 or more elements chemically combined (bonded) • Why bond? 1. Atoms bond to become stable 2. It requires a full outer shell to be stable 3. 8 valence electrons = an octet Metals vs. Nonmetals Types of bonds Covalent bonds – bonds btwn two nonmetals Types of bonds Ionic bonds – bonds btwn a nonmetal & metal Types of bonds Metallic bonds – bonds btwn two metals Mixtures • Mixtures - 2 or more elements occupying the same space – Homogeneous mixtures – substances can’t be easily identified • Ex/ Kool-Aide, coffee, paint – Heterogeneous mixture – substances can be easily identified • Ex/ chicken noodle soup, cereal, & the atmosphere