What is the main type of intermolecular forces in PH3?

PH3, otherwise known as phosphine and is quite toxic and flammable, forms a dipole-dipole because it is a polar molecule. We know it is polar because it has a lone pair and therefore its geometry is non-symmetrical as predicted by the VSEPR model.

Nonpolar molecules have a symmetrical distribution of charge, and the London dispersion is the weakest intermolecular force. Molecules with H-F, H-O, or H-N (because of big EN) are known as hydrogen bonding; saltwater (ionic compound and water) are known as non-dipole forces. Since PH3 is a polar molecule without H-F, H-O, or H-N, this qualifies as having dipole-dipole forces.