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CHEMICAL BOND FORMATION

CHEMICAL BOND FORMATION. Ionic Bonds. an electrostatic attraction between ions -- usually the reaction between a metal and nonmetal . Cause very high melting points and usually a solid state since the attraction is SO strong that the ions are VERY close

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CHEMICAL BOND FORMATION

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  1. CHEMICAL BOND FORMATION

  2. Ionic Bonds an electrostatic attraction between ions -- usually the reaction between a metal and nonmetal. Cause very high melting points and usually a solid state since the attraction is SO strong that the ions are VERY close together in a crystal formation.

  3. Covalent Bond Bond orbital is more or less (polar or non-polar) evenly distributed and the electrons are shared by two nuclei. (Elements lie close to one another on the table.)

  4. Electronegativity (En) The ability of an atom IN A MOLECULE [meaning it’s participating in a BOND] to attract shared electrons to itself. Think “tug of war”.

  5. Linus Pauling’s Scale Nobel Prize for Chemistry & Peace

  6. What’s the trend? Fluorine is the most En (Highest Zeff and smallest so that the nucleus is closest to the “action”) & Francium is the least En(Lowest Zeff and largest so that the nucleus is farthest from the “action”)

  7. Use the difference in En to determine the type of bond formed.

  8. a. Covalent , equally shared electrons b. Polar Covalent, slight +/- poles c. IONIC, electrons are transferred from one atom to another

  9. The polarity of a bond can be estimated from ΔE/Highest E. Range is 0 for pure covalent bonds, to 1 for completely ionic bonds.

  10. Exercise 1 Relative Bond Polarities Order the following bonds according to polarity: H—H O—H Cl—H S—H F—H

  11. Solution

  12. Practice Problems • Using only periodic trends of electronegativity, predict the order of increasing electronegativity difference between following bonds: • C-F; Si-F; Ge-F • S-F; S-Cl; S-Br • Ti-Cl; Si-Cl; As-Cl • Ga-Br; Sb-Br; Tl-Br; Mg-Br;

  13. Solutions • Ge-F; Si-F; C-F • S-Br; S-Cl; S-F • Ti-Cl; Si-Cl; As-F • Tl-Br; Sb-Br; Ga-Br; Mg-Br Study Guide Problems to try: Ch. 8: 4-10 & 43-46

  14. What is a DIPOLE and what does it mean? • A Dipole is Di= 2 and pole= + & - end • In a diatomic molecule like H-F there is partial; positive and partial negative charge • To show the dipole we draw an arrow pointing at the negatively charged particle. • H-F the tail starts at the more positive end

  15. Examples and steps • Look up E. N. for each atom • Draw the molecule in 3-d (yes you have to do this again) • Determine the net polarity on each bond • Draw the dipoles, with correct direction • HI; CHCl3; CF2I2’ ; N2

  16. Solutions • H-I H=2.1 I=2.5 • C= 2.5 H=2.1 Cl=3.0 • H • C • Cl Cl Cl • N-N N=3.0 Diff= 0 no dipole I • C= 2.5 l= 3.0 F= 4.0 C • F F I • Problems to try in study guide: 11-13 and 47-48

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