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Monday November 5, 2012

Monday November 5, 2012. (Worksheet - Ionic Bonds, the Octet Rule, and Lewis Structures). Bell Ringer Monday, 11-5-12. Oxygen forms covalent bonds with  carbon and sulfur, but forms ionic bonds with sodium and magnesium. What is the BEST inference for this difference in how oxygen behaves?

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Monday November 5, 2012

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  1. MondayNovember 5, 2012 • (Worksheet - Ionic Bonds, the Octet Rule, and Lewis Structures)

  2. Bell RingerMonday, 11-5-12 Oxygen forms covalent bonds with  carbon and sulfur, but forms ionic bonds with sodium and magnesium. What is the BEST inference for this difference in how oxygen behaves? A Oxygen bonds randomly with elements in unpredictable  ways . B The difference in atomic radii between the groups accounts for the difference in behavior . C Oxygen only bonds with elements that have a smaller atomic mass. D Electronegativity differences between the bonding elements allow electrons to be either shared or donated.

  3. Announcements Happy November

  4. Ionic Bonds Na+ A sodium ion, Na+, has a charge of 1+. Cl- A chloride ion, Cl−, has a charge of 1−.

  5. Ionic Bonds Na+ Cl- In sodium chloride, these ions combine in a one-to-one ratio (Na+Cl−) so that each positive charge is balanced by a negative charge, resulting in a neutral charge for the unit as a whole. The chemical formula for sodium chloride is usually written simply as NaCl. Na Cl

  6. Ionic Bonds An ionic compound is composed of positive and negative ions that are combined so that the numbers of positive and negative charges are equal. Na Cl2 Cl Mg

  7. Ionic Bonds Example Sodium has 1 valence electron and loses it to become stable, but in doing so takes on a 1+ charge. Na → Na++ e- Chlorine has 7 valence electrons and gains 1 to become stable, but in doing so takes on a 1- charge. • e- + Cl→Cl- Na++Cl-→NaCl The two oppositely-charged ions attract each other and form an ionic bond. The compound is neutral.

  8. Dot Notations of Na and Cl

  9. Ionic Bonds Example Calcium has 2 valence electrons and loses them to become stable, but in doing so takes on a 2+ charge. Ca→Ca2++2e- Two fluorine atoms have 7 valence electrons each and each gains 1 to become stable, but in doing so both take on a 1- charge. • 2e- + 2F→2F- Ca2++2F-→CaF2 The calcium ion attracts both of the fluoride ions and form an ionic bond. The compound is neutral.

  10. Dot Notations of Ca and F In order to be neutral, this compound must exist in a 1:2 ratio. CaF2

  11. The Octet Rule Noble Gas atoms normally exist singly in nature. The reason for this is because they have a completely filled valence shell (outer lane.) He has 2 electrons in its valence shell, while all other NG’s have 2 in their s-orbital and 6 in their p-orbitals for a total of 8 electrons. This configuration is what is needed to be stable. All other atoms must fill their valence shells through bonding.

  12. The Octet Rule Bond formation follows the Octet Rule, which states that chemical compounds tend to form so that each atom, by gaining, losing or sharing electrons, has an octet of electrons (8) in its highest occupied energy level.

  13. The Octet Rule For example , fluorine has an electron configuration notation of 1s2, 2s2, 2p5 In fluorine’s highest occupied energy level it has 2 electrons in the s sublevel and 5 electrons in the p sublevel. The total number of electrons in fluorine’s highest occupied energy level is therefore 2 + 5 = 7 One fluorine atoms bonds to a second fluorine atom to form F2 (fluorine gas, a compound). Each atom shares one of its valence electrons with its partner to get 8 electrons in the valence shell.

  14. The Octet Rule Fluorine The shared electron pair effectively fills each atom’s outermost energy level _____ _____ _____ _____ _____ 1s2 2s2 2px 2py 2pz _____ _____ _____ _____ _____ 1s2 2s2 2px 2py 2pz

  15. Electron-Dot Notation In compounds, a pair of dots between two symbols represents the shared pair of electrons. An unshared pair (lone pair) is a pair of electrons that is not involved in bonding and that belongs exclusively to one atom. The pair of dots representing a shared pair of electrons in a covalent bond is often replaced by a dash.

  16. Lewis Structures Electron Dot Notation representations are termed Lewis Structures. Lewis Structures are formulas in which: • an element’s atomic symbol represents its nuclei and inner-shell electrons. • dot pairs or dashes between two atomic symbols represent valence electron pairs in covalent bonds. • dots adjacent to only one atomic symbol represent unshared valence electrons.

  17. Lewis Structures Lewis structural formulas indicate the kind, number, arrangement and bonds but not the unshared pairs of the atoms in a molecule. F-F H-Cl A covalent bond produced by the sharing of one pair of electrons between two atoms is called a single bond.

  18. Lewis Structures ExampleDraw the Lewis structure of iodomethene, CH3I The formula shows one carbon atom, one iodine atom, and three hydrogen atoms. Write the electron-dot notation for each type of atom in the molecule. Carbon is in Group 14 and has four valence electrons. Iodine is in Group 17 and has seven valence electrons. Hydrogen above Group 1 has one valence electron.

  19. Worksheet Ionic Bonds, the Octet Rule, and Lewis Structures

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