Unit 5

ionic bond

electrostatic attraction between positive and negative ions

transfer of electrons

from metal to nonmetal

strength of ionic bonds

smaller ions = stronger bond

greater magnitude of charge = stronger bond

polar covalent bonds

difference in EN

unequal sharing of electrons, dipoles

between 2 different nonmetals

nonpolar covalent bonds

no difference in EN

equal sharing of electrons, no dipoles

between 2 of the same nonmetal or when the difference in EN is 0.4 or below

VSPER theory

Valence Shell Electron Pair Repulsion

electron domains around the central atom repel and get as far apart as possible

2 bonding domains, 0 nonbonding domains

linear, linear (180 degrees)

3 bonding domains, 0 nonbonding domains

trigonal planar, trigonal planar (120 degrees)

2 bonding domains, 1 nonbonding domains

trigonal planar, bent (118 degrees)

4 bonding domains, 0 nonbonding domains

tetrahedral, tetrahedral (109 degrees)

3 bonding domains, 1 nonbonding domains

tetrahedral, trigonal pyramidal (107 degrees)

2 bonding domains, 2 nonbonding domains

tetrahedral, bent (105 degrees)

bond polarity

in an individual bond, one side is more negative than the other

molecule polarity

the polarity of the molecule as a whole taking into account:


1. bond polarities
2. the shape of the molecule

there are dipoles in the molecule and the bond dipoles don’t cancel

polar molecule

there are dipoles in the molecule and the bond dipoles do cancel

nonpolar molecule

there are no dipoles in the molecule

nonpolar molecule

polar molecules IMFs

hydrogen bonding (if H + N,O,F)

dipole-dipole forces (not hydrogen bonding)

nonpolar molecules IMFS

london dispersion forces

lower strength IMFs

high evaporation rates, low boiling/melting point, easy to go from solid-liquid-gas

higher strength IMFs

low evaporation rates, high boiling/melting point, hard to go from solid-liquid-gas

why hydrogen bonds are strong

H,N,O,F are all very small atoms

big difference in EN between H and N,O,F

affecting the strength of LDFs

lots of electrons = strong LDF

shape of molecule