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Electronegativity

http://www.bing.com/images/search?q=don%27t+you+think+i%27d+know+it+sheldon+big+bang+picture&FORM=HDRSC2&adlt=strict#view=detail&id=148557739FB1060AF6F3DB1FDBC3D16A20678015&selectedIndex=1. Electronegativity. Electronegativity is the ability of an atom to attract electrons.

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Electronegativity

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  1. http://www.bing.com/images/search?q=don%27t+you+think+i%27d+know+it+sheldon+big+bang+picture&FORM=HDRSC2&adlt=strict#view=detail&id=148557739FB1060AF6F3DB1FDBC3D16A20678015&selectedIndex=1http://www.bing.com/images/search?q=don%27t+you+think+i%27d+know+it+sheldon+big+bang+picture&FORM=HDRSC2&adlt=strict#view=detail&id=148557739FB1060AF6F3DB1FDBC3D16A20678015&selectedIndex=1

  2. Electronegativity • Electronegativity is the ability of an atom to attract electrons. • The electronegativity scale was devised by Linus Pauling. • It is an arbitrary scale with Fluorine (the most electronegative element) having a value of 4. • All other electronegativities are assigned relative to Fluorine. • Why Fluorine??

  3. Electronegativity • Differences in electronegativity between two atoms can tell you what type of bond will form between those atoms. • If two atoms have similarelectronegativities, neither is stronger than the other. They will share electrons equally… this is a covalent bond.

  4. Electronegativity • If two atoms have somewhat differentelectronegativities, one atom is slightly stronger than the other. They will share electrons UNequally… this is a polar covalent bond. • They are still sharing electrons, but the electrons spend more time around the more electronegative atom (giving it a slight negative charge), and less time around the less electronegative atom (giving it a slight positive charge) creating a dipole.

  5. Electronegativity • If two atoms have very differentelectronegativities, one atom is much stronger than the other. The stronger atom will take the electron(s) from the other atom. This is an ionic bond. • The atom that takes the electron(s) becomes a negative ion. • The atom that gives up the electron(s) becomes a positive ion. • The ions are attracted to each other and form a crystal lattice.

  6. Predicting types of bonds…

  7. Electronegativity • What trends do you see in electronegativity? • What type of bonds form when atoms from opposite sides of the periodic table for a compound?

  8. Trends in Electronegativity Electronegativity Increases Highest Electronegativity Decreases Lowest

  9. Questions • P&P #1 p. 131: Make a Venn diagram to compare and contrast Ionization and Electronegativity • P&P #3a p. 134: Make a diagram to show how each pair of atoms listed below shares or transfers electrons and determine the type of bond: • Hydrogen – Oxygen in water • Carbon – Oxygen in CO2 • Potassium – fluorine in KF • Carbon – Hydrogen in CH4 • Bromine – Bromine in Br2

  10. P&P #3 • H-O bond in water H20 • C-O bond in Carbon dioxide • K-F bond in KF O 3.5 H 2.1 1.4 Polar Covalent H O Electrons closer to Oxygen H Electrons closer to Oxygen O 3.5 C 2.5 1.4 Polar Covalent C O O F 4.0 K .8 3.2 Ionic K F Electrons closer to Fluorine

  11. P&P #3 • C-H bond in methane CH4 • Br-Br bond in Bromine C 2.5 H 2.1 .4 Covalent C H Electrons almost in the middle Br 2.8 Br 2.8 0 Covalent Br Br Electrons are in the middle

  12. Venn Diagram Electronegativity is the tendency of an atom to ATTRACT electrons in a bond Both have tendencies to want electrons Same trends in the periodic table Ionization is the energy needed to REMOVE an electron

  13. Reflect and Connect • 1. Predict what type of molecule (or compound) each of the following might be, justify: • A) CaCl2 • B) N2 • C) CO2 • 2. Describe in your own words how bonding atoms contributes to the characteristics of an entire molecule or group of atoms.

  14. Reflect and Connect • Predict what type of molecule (or compound) each of the following might be, justify: • A) CaCl2 • B) N2 • C) CO2 • CaCl2 is ionic, this is because Ca and Cl are on opposite ends of the Periodic Table. • Ca carries a positive charge • Cl carries a negative charge • N2 is covalent because they have the same electronegativity, ionization energy, and are the same element • CO2 is covalent because they have the similar ionization energies and are near each other in the Periodic Table

  15. Reflect and Connect • 2. Describe in your own words how bonding atoms contributes to the characteristics of an entire molecule or group of atoms. Bonding inside a molecule affects the entire molecule because bonds effectively distribute charge that charge in the molecule.

  16. Balance Chemical Equations • http://www.youtube.com/watch?v=HB6cG7bQew0&feature=youtu.be • WKST

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