2.2.8 Intermolecular forces

what are intermolecular forces

froces of attraction between molecular covalent compoudns that must be overcome when melted or boiled

what are the 3 types of intermolecular forces from least to most strong

london dispersion forces

dipole dipole forces

hydrogen bonding

electrons are in a constant state of motion. what does this mean

at any given time the distribution of electrons is likely to be not exactly symmetrical

what is this known as

temporary or instantaneous dipole which has a temporary partial positive and negative part of the molecule

what happens to the adjacent atom

the electrons are repelled by the partial negative part of the instantaneous dipole so move, inducing a partial charge and forming an induced dipole

between what atoms are london dispersion forces present

between all atoms and molecules

what does the strenght of the london dispersion forces depend on

the number of electrons (molar mass)

surface area of the molecules

how does the number of electrons or the molar mass affect the strength

more electrons, greater likelyhoodof instantaeous dipole and the greater the magnitude and frenquency of the instantaneous dipole

summarise this

grreater molar mass or number of electrons, greater strength london dispersion forces and so greater m and b points

how does the surface area affect this

greater the surface area, greater the contact with adjacent molecules and the greater its ability to induce a dipole in the next molecule so greater the LDF and greater m and b points

where is permanent dipole dipole bonding present

between polar molecules with a net dipole moment

what effect does dipole dipole bonding have on the m and boiling points and why

larger when compared to only LDF because increases the strength of intermolecular attractions

what are dipole induced dipole dorces

when the permanent dipole of one molecule causes a temporary seperation of charge from another non polar molecule

what forces are present in a polar molecule

LDF and dipole dipole forces

what is hydrogen bonding a special type of

permanent dipole dipole bonding

what 3 elements and hydrogen are needed for hydorgen bonding

nitrogen

oxygen

flourine

what else is needed

a lone pair of electrons on the N O F molecule

what happens when hydrogen bonded to these highly electronegative atoms

the bond becomes highly polarsied and atoms gain partial positive and negative charges

what 2 forces do van der waals forces include

london dispersion forces and diploe dipole forces

what is intramolecular

within a moleucle

what is intermolecular

between molecuels

what types of forces do atoms with hydrogen bondign also contain

LDF, dipole-dipole forces and hydrogen bonding