hey Frank Ose,
im not a teacher. you have to consider the effect of the relative size of the atom. A smaller atom would have higher electron density because the electrons occupied a smaller volume. Therefore what consequences does it have on the requirement of hydrogen bonding?
I know the size of the electronegative atom has to be considered.But I do not know why it has to be considered and I can't think of the consequences. Any logical explanation on how the size of electronegative atom affects the formation of hydrogen bond?
This is my understanding at the moment, correct me if this is erroneous.
A smaller atom would have higher electron density, thus attracting the barely shielded atom more strongly.In this case, N atom in NH3 is smaller and so the barely shielded H atom from other NH3 molecule can approach it closer and form hydrogen bond with it.And for HCl,electronegative Cl is bigger in size, hence the electron density is scattered and thus less strong than that in NH3. Therefore, the barely shielded H atom in HCl could hardly approach the electronegative Cl of other similar molecules because the attraction is not strong to hold them together.
Thanks in advance.