How many lone pairs of electrons (electrons that are not involved in bonding) are on the nitrogen in HCN?

Both models are effective because they show the valence electrons, and these valence electrons indicate the reactivity of an element.

Ch4 and ph3 are both covalent since they are composed both of non-metals.    ch4 is non- polar because of  london forces and has a geometry of tetrahedral  ph3 , on the other hand, is umbrella shaped polar and has dipole-dipole intermolecular force (imf) . since ph3 is polar, it has a stronger imf