intermolecular forces Flashcards
what state will the molecule be if the intermolecular forces are very strong ?
liquids or solids
name the three types of intermolecular forces ?
Van der waals forces
dipole-dipole forces
hydrogen bonding
what is dipole moment ?
the meaure of net polarity
what has happened in a molecule with no dipole moment ?
in a molecule with more than one polar bond , the effects of each bond may cancel .
what do dipole moments depend on ?
the shape of molecules
How do you tell if a dipole moment has cancelled out ?
electron density evenly spread
what do dipole dipole forces act between ?
molecules with permanent dipoles
will two molecules that have dipoles attract one another?
yes and they will flip to give an arrangement where the two molecules attract
describe van der waals forces ?
all atoms and molecules are made up of positive and negative charges even though they are neutral overall . Their weak electrostatic attractions between theses charges called Van der waals forces
how do Van der waals forces work ?
electrons are constantly moving , therefor constantly creating new dipoles . This causes the other atoms to be attracted to the original atom and creates induced dipoles .the forces between these dipoles are called van der waals forces
where do van der waals forces act ?
between all atoms and molecules at any time
what increases the size of instantaneous dipole ?
the amount of electrons
why does the boiling points of noble gas increase as the atomic number of noble gas increases ?
atoms with a higher atomic mass have more electrons and therefor produce strong van der waals forces
why do the boiling points of hydrocarbons increase with chain length
a higher molecular mass = stronger van der waals forces
what is a hydrogen bond ?
a hydrogen atom covantley bonded to a very electronegative atom ( F,N ,O)which has a lone pair
