Covalent bond

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  • Quartz (silicon dioxide) is the most common mineral species in the earth's crust.
    http://www.minvision.com/mvpics/0275331001148477692730993.jpg
    http://ftp.gnome.org/pub/GNOME/teams/art.gnome.org/backgrounds/NATURE-QuartzSand_1024x768.jpg
    http://en.wikipedia.org/wiki/Image:Third_beach_sand.jpg
  • Covalent bond

    1. 1. Covalent Bonding
    2. 2. Chemical Bonding …atoms share electrons to get a full valence shell Covalent Bonds C 2s2 2p2 (4 v.e– ) F 2s2 2p5 (7 v.e– ) both need 8 valence electrons for a full outer shell (octet rule) 1s2 1s2
    3. 3. Covalent bonding F F • Fluorine has seven valence electrons • A second F atom also has seven • By sharing electrons • Both end with full orbitals (stable octets) 8 Valence electrons 8 Valence electrons
    4. 4. Covalent Bonding - - - - n = 1 O [He]2s2 2p4 n = 2 + - - - - - - - O2 Sharing of electrons to achieve a stable octet (8 electrons in valence shell). - - - - - - - - - - - - - - - - - O [He]2s2 2p4
    5. 5. Covalent/Molecular Compound Silicon dioxide, SiO2, is a molecular compound. It is also a mineral called quartz (left). Quartz is found in nearly every type of rock. Most sand grains (center) are bits of quartz. Glass is made from sand. A compound containing atoms of two or more elements that are bonded together by sharing electrons.
    6. 6. Covalent Bonding - True Molecules Types of Bonds Diatomic Molecule Ammonia Nitrogen Water
    7. 7. Covalent vs. Ionic Covalent Transfer electrons (ions formed) + / - Between Metal and Nonmetal Strong Bonds (high melting point) Share electrons (polar vs. nonpolar) Between Two Nonmetals Weak Bonds (low melting point) Alike Different Electrons are involved Chemical Bonds Ionic Different Topic Topic
    8. 8. Lewis Structure Lewis structure: a model of a covalent molecule that shows all of the valence electrons 1. Two shared electrons make a single covalent bond, four make a double bond, etc. 2. unshared pairs: pairs of un-bonded valence electrons 3. Each atom needs a full outer shell, i.e., 8 electrons. Exception: H needs 2 electrons
    9. 9. Lewis Structure carbon tetrafluoride (CF4 ) o C o o o x xx x x x F x o C o o ox xx x x x F x x x x x x x F x x xx x x F x x x xx x x F x x Cx xx x x x F x x x x x F x x xx x F x x xx x x F x x covalent compounds = molecular compounds (have lower melting points than do ionic compounds)
    10. 10. Lewis Structure o Co o o x H o Co o oH x x H x H x H CH H H H x xx x x x I x o No o o o o No o ox xx x x x I x x x x x x x I x x xx x x I x x o o Nx xx x x x I x x x x x I x xx x x I x x o o Co o o x xx x x O x x xx x x O x x xx x x O x o Co o o O = C = O x x x xx x x x methane (CH4 ) carbon dioxide (CO2 ) nitrogen triiodide (NI3 )

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