bonding - 3.5 forces acting between molecules

Question 1

what are the 3 types of intermolecular forces and what are they between

Answer 1

van der waals forces
-act between all atoms and molecules

dipole-dipole forces
-act only between certain types of molecules

hydrogen bonding
-act only between certain types of molecules

Question 2

describe van der waals forces in terms of strength

Answer 2

-the weakest type of intermolecular force
-it acts as an induced dipole between molecules
-the strength varies depending on the size of the molecule, the bigger number of electrons, the stronger the van der waals force

Question 3

why do van der waals forces occur

Answer 3

-because the electrons are constantly moving around and there will be an uneven electron distribution at any given moment in time. this causes a temporary dipole within a molecule
-this temporary dipole induces a temporary dipole in a neighbouring molecule. there is then an attraction between these molecules (a temporary induced dipole-dipole attraction)

Question 4

where do permanent dipole-dipole forces occur

Answer 4

there are permanent dipole-dipole attractions between polar molecules

Question 5

describe hydrogen bonding

Answer 5

-this intermolecular force occurs between 2 very electronegative atoms atoms (fluorine, oxygen and nitrogen atoms only) which are bonding to a hydrogen atom
-this is a strong intermolecular force, not a bond