intermolecular forces

van der Waals’ forces

intermolecular forces

electronegativity

power of a particular atom that is covalently bonded to another atom to attract the bonding pair of electrons towards itself

greater value of electronegativity

greater the power of an atom to attract covalently bonded electrons towards itself

patterns of electronegativity

increases across a period…decreases down a group

nuclear charge

atoms in the same period with a greater nuclear charge are more electronegative

atomic radius

atoms in the same group with electrons further from the nucleus are less electronegative

shielding

greater the number of inner electron shells and sub-shells, the lower the electronegativity

polar bonds

electron pair in the bond is drawn towards the atom with the larger electronegativity, making one end of the molecule slightly positive compared to the other

bond polarity

partial separation of charge when two different atoms covalently bond…results in unequal attraction between bonding pairs

instantaneous dipole - induce dipole forces

weakest intermolecular force…results from temporary dipoles induced in both polar and non-polar molecules

id-id forces increase with

increased electron number…increased contact points between molecules

contact points

places where the molecules come close together

permanent dipole-permanent dipole forces

attractive intermolecular forces which result from permanent dipoles in molecules