Chemistry - Shapes of moleculesWatch
In order for a molecule to be polar, two elements must have a large difference in electronegativity (usually bigger than 0.5). As the difference between H and As is 0.1, the dipoles cancel out, and the molecule is considered non-polar.
Hi! So dipole-dipole interactions are caused by attractions between polar molecules. In order for a molecule to be polar there must be a large difference in electronegativity causing one atom to pull the electron density towards itself e.g. in water there is a large difference in electronegativity between the oxygen and the hydrogen in the O-H bonds hence oxygen pulls the electron density towards itself giving the oxygen a delta - charge and hydrogen a delta + charge hence it forms dipole-dipole intermolecular forces with other H2O molecules. There is not a large enough difference in electronegativity between As and H in the As-H bond so no permanent dipole forms hence dipole-dipole interactions don’t occur between AsH3 molecule and so the only intermolecular forces are VdW forces. Hope that helps. Let me know if u need any more clarification. Xx