Intermolecular Forces

Intermolecular Forces

forces going on between molecules that already exist

The 3 intermolecular forces are

London Dispersion forces, Hydrogen bonding & Dipole-Dipole moments

HOMO

highest unoccupied molecular orbital

LUMO

lowest unoccupied molecular orbital

Dipole

uneven electron density distribution in an atom, making it polar or non-polar

Dipole -Dipole Interactions are

molecules with permanent dipoles (polar molecules) orienting themselves so that delta pos and delta neg are facing another.

Dipole Dipole Interactions only happen when

both molecules are polar

London Dispersion is in

ALL MOLECULES

London Dispersion is the only thing at play

in non polar bonds

London Dispersion forces are

weak

London dispersion forces means

instantaneous dipole, inducing a dipole moment in another molecule

London Dispersion is related to

polarizability

Induced dipole

electrons moving in response to an outside force and this happen usually to non polar molecules

If a molecule is more polar,

the attraction between each atom is stronger, meaning it takes more energy to get them into the gas phase, liquid, or solid phase.

When determining if a molecule is polar

look at shape & dipole vector cancellation

the bigger and more polarizable an atom

the more London dispersion forces are at play, meaning that they require more energy to break

the higher the atomic weight

the higher the melting point (explain)

Intermolecular forces impact

the attraction between molecules to each other, impacting properties

When determine boiling point, and mp, we must consider

shape/size, molar mass, polarizability, & intermolecular forces play

IMFs increase as

molecular weight increases

When comparing molecules of roughly comparable size

Dipole Dipole Forces are significant

when comparing molecules of diff sizes

London Dispersion forces are most important