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

 the atoms in the bond pull the shared pair of electrons equally  Ex. H 2, O 2, N 2, and Cl 2

 atoms in the bond pull the shared pair of electrons unequally  Ex: HCl, H 2 O

BF 3

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 +)

covalent, non-polar covalent, polar ionic

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

H2OH2O  CO 2  CH 3 Cl  CCl 4

non-polar polar

 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

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