6.3 Intermolecular forces

define intermolecular forces

weak interactions between dipoles of different molecules

describe how London forces form

1) electrons in a molecule move which changes the dipole and an instantaneous dipole occurs

2) the instantaneous dipole induces a dipole on the neighbouring molecule

3) the induced dipole induces dipoles on neighbouring molecules which then attract each other

what increases the strength of attractive forces between molecules

the increase of number of electrons in a molecule

describe a permanent dipole

a partially negatively charged area of one molecule is attracted to a partially positively charged area of another molecule

describe a simple molecular lattice in terms of bonding

the molecules are held together by weak intermolecular forces but the atoms within each molecule are held together strongly by covalent bonds

explain why simple molecular compounds are soluble in non-polar solvents

1) smc and non polar solvents mix to form imf between the smc molecules and the molecules in the solvent

2) these weaken the weak imf in the simple molecular lattice

3) the weak imf in the sml break

4) the smc dissolves

explain why simple molecular compounds are insoluble in polar solvents

the intermolecular bonding within the polar solvent is too strong

order of strength of intermolecular forces

hydrogen bonds > permanent dipole-dipole interactions > London forces