Intermolecular Forces

What are intermolecular forces

The attractive forces between neighbouring molecules

What do intermolecular molecules control

Physics properties such as melting or boiling point

Relative strength to covalent bonds

Weak

What are intermolecular molecules caused by

Weak attractive forces between very small dipoles in different molecules

What’s the difference between Inter and intra molecular forces

Inter is between molecules intra act within 1 molecule

2 types of intermolecular forces

van der waals and hydrogen

Types of van ser walls forces

Permanent dipole dipole, permanent dipole induced dipole, london dispersion forces

Permanent dipole- permanent dipole interactions

Are a weak attractive force between permanent dipoles in neighbouring pole molecules

What kind of molecules have a permanent dipole

Polar molecules

How do permanent dipole permanent dipole interactions work

The permanent dipole of one molecule attracts the permanent dipole of another

Permanent dipole- induced dipole forces

A weak attractive force that occurs when a polar molecule induces a dipole in a neighbouring non polar molecule

how do permanent dipoles induce dipoles

when permanent dipoles are near non polar molecules they cause the electrons to shift slightly by either being repelled or attracted causing an induced dipole in that molecule

london dispersion forces

attraction between instantaneous dipoles

how do london dispersion forces occur

at any moment oscillations produce an instantaneous dipole which induce dipoles in neighbouring molecules. the induced dipoles attract one another

relative strength of london dispersion forces

the weakest intermolecular force

simple description of london dispersion forces

electrons are constantly moving within molecules so can be at either end at any one moment which cause temporary dipoles that can cause induced dipoles in neighbouring molecules which cause an attraction

where are london dispersion forces always found

in covalent molecules

what kind of molecules do london dispersion forces occur between

non polar molecules

factors affecting the strength of LDF

number of electrons, distance between molecules, surface area of molecule

how does the number of electrons affect the strength of LDF

more electrons= stronger LDF

how does distance between molecules affect the strength of LDF

the closer the molecules the closer the LDF so the stronger they are

example of how distance affects strength of LDF

flat, long chain molecules can get closer together so they have more LDFs than branched molecules with the same number of electrons

how does surface area affect the strength of LDF

the greater the surface area the more contact between molecules= more LDFS

what kind of elements experience LDFS

monoatomic elements (noble gases)