non-covalent forces

intramolecular forces occur…

within same molecule (protein folding)

intermolecular forces occur…

between 2 separate molecules (DNA hydrogen bonding)

how much weaker are non-covalent forces than covalent or ionic bonds ?

10 - 50x

what forces attract neutral molecules to each other ?

electrostatic

what is meant by the dipole moment

overall polarity of a molecule

dispersion forces

movement of electrons within orbital causes an uneven distribution of charge causing + and - areas of molecules to attract (induced dipole)

characteristics of dispersion forces

short lived, weak, require close proximity

polar molecules…

have permanent dipole

hydrophobic forces

dispersion forces that occur between hydrophobic regions of a molecule eg.protein during structural rearrangement to shield them from aqueous environment

permanent dipolar interactions

attractive forces that exist between opposite partial charges on polar molecules with permanent dipoles

induced dipolar interactions

permanent dipole of one molecule can induce dipole on another non-polar molecule therefore generating attraction

hydrogen bonds

dipolar interaction where one partner is H and the other is a strongly electronegative atom with at least 1 pair of lone electrons

Van der Waals interaction

overall effect of 3 distinct molecular interactions - dispersion forces, permanent dipolar interactions and steric repulsion

ionic interactions

attraction between ionic species formed as a result of permanent electron transfer

steric repulsion

initial repulsion that occurs when 2 molecules are attracted due to electron clouds

entropy

measure of system's thermal energy (per unit) that is unavailable for doing useful work