Bond Polarity and Molecules

1. Bond Polarity and Molecules

2. Polarity • shared bonding electrons pairs are pulled (as in a “tug-of-war”) between atoms • results in an equal or unequal sharing

3. Nonpolar covalent bonds • the atoms in the bond pull the shared pair of electrons equally • Ex. H2, O2, N2, and Cl2

4. Polar Covalent Bonds • atoms in the bond pull the shared pair of electrons unequally • Ex: HCl, H2O

5. BF3

6. more electronegative atoms have a greater attraction for electrons • gives that “side” of the molecule a slightly negative charge (δ -). • less electronegative atoms therefore have a slightly positive charge (δ +)

9. What does electronegativity have to do with polarity?

10. covalent, non-polar covalent, polar ionic

11. electronegativty difference probable type of bond 0.0 – 0.4 covalent, nonpolar covalent, slightly polar 0.4 – 1.0 covalent, very polar 1.0 – 1.7 ionic ≥ 1.7

12. Practice problems • H2O • CO2 • CH3Cl • CCl4

13. polar non-polar

14. Attractions Between (not within) Molecules • Van der Waals Forces – polar molecules attracted to one another • positive ends are slightly attracted to negative ends • weakest of attractions between molecules • often determines whether a substance is a solid, liquid, or a gas

15. hydrogen bonding • occurs when positively charged hydrogens are weakly attracted to the unshared electron pairs of another electronegative atom. • stronger than Van der Waals

17. Hydrogen Bonding in Nature