intermolecular forces

Electronegativity

The ability of an atom to attract the bonding electrons in a covalent bond

Electronegativity increases across periods up the group- smaller atomic radiii

How do differences in Electronegativity affect covalent bonds

Bonding electrons will be pulled mire towards the more electronegative atom so the electrons are spread unevenly and there are partial charges

Dipole

Difference in charge between two atoms caused by a shift in electron density

Intermolecular forces

1. London forces

2. Permanent dipole dipole

3. Hydrogen bonding

London forces

Cause all atoms and molecules to be attracted to each other

Dipole induces more dipoles in other

Hold molecules together in a lattice

Larger molecules hve larger electron clients so stronger London forces

Molecules w greater surface area have stronger London forces- bigger exposed electron cloud

Branched alkanes and London forces

Can’t pack closely so their molecular surface contact is small so less London forces

Permanent dipole dipole bonds

Attraction between molecules w differences in Electronegativity, WITH London forces

Hydrogen bonding

Strongest force, only when hydrogen us cov bonded to fluorine, nitrogen or oxygen

Hydrogen has high charge density,