Chemistry Intermolecular forces question??

Question

I'm going to ask this one more time because I didn't get an answer....Based on dispersion forces, dipole-dipole, and other intermolecular interactions, how come BeO's melting point is so much higher than BaSO4?

Answer 1

This is an extremely hard to anwer question:
let's see Be is a metal, with a very small radius, it's oxide should have a bcc body centered cubic lattice structure, this should bring the distance between Be and O really close
Be-Be distance in the metal is 202 pm, really short, Be-O should be shorter. Moreover the great eletronegativity diference should bring a strong binding between Be and O, nearly 100% of ionic bond. In fact BeO is one of the highest melting ceramic known.

Barium is instead a really huge metal, with a distance in the metal of 437 pm, really long distance, in fact Barium is a low melting metal with only 720°C of mp.
he sulfate ion contains 4 covalent bonds, and is very big ion.
Crystal System is orthorhombic (barite), this bring the distance of the barium and the sulfate ion to a relatively long distance with a higher character of covalent bond then ionic bond, with a lot of holes for smaller ions to fix the holes (lithum and sodium sulfate mixed minerals with barium are quite classic) Holes means space, space means possibility of polimorphism, and means possibility to the ions to "move" when the temperatures are high (hundred of degrees), this means that barium sulfate has a low melting point.

For a more physical explanation (atom-atom interactions) you need someone with more experience in physics then in chemistry, sorry. I'm just a chemist.

Answer 2

a) naphthalene molecules exist in stable state held jointly by employing intermolecular forces that are in part triumph over while the mothball is melted right into a liquid. b)HBr further to water comprises breaking covalent bonds H-Br + H-O-H --------> Br^- + ( H-O-H)^+ / H c) Vaporizing ethyl alcohol comprises overcoming intermolecular forces to variety gaseous ethyl alcohol d)changing Ozone to oxygen comprises breaking and reforming covalent bonds