[lorenalareyna]

When a molecule structure has 0 nonbonding electros pairs does that mean that it's nonpolar?

[nj_bartel]

I want to say no, but I'm having trouble coming up with a counterexample.

[qstong0601]

it dosent necessarily mean that all the valence electrons are used up, it is a non polar molecule.
the polarity of the molecule depends on many factors like the shape and the components of the elements.
exemples:CH4  there are four bonding pairs, and no lone pairs, that means all of the valence electrons are used to form covalence bonds. and the 3D shape of CH4 is tetrahedral where all the dipoles of the same two elements cancle out. so, CH4 is a non polar molecule.

CF3Cl   in which C is the central atome, there are 4 bonding pairs around it. the shape of the molecule is tetrahedeal, which is symetrical about the central atom. but electronegativity between C and F and C and Cl are different.the dipole cannot cancel out each other. the net dipole is not not 0. so we say CF3Cl is a polar molecule, although all of the valence electrons of the central atoms are used up to form the covalent bonds

[nj_bartel]

That's not the question though.  The question is 'if a given compound has 0 nonbonding electrons, is it nonpolar?'

[qstong0601]

oh, i misunderstood the question... then i think the answer to the question is no. the counterexeple maybe C3H6-propane. the shape of propane is not symetrical in 3D. two trigonal plannars and one tetrahedral constitute the shape. since its not geometrically symmetric,the dipoles dont cancel out, we now cans say the hypothesis is not true.
is that right?

[nj_bartel]

There aren't any significant dipoles in propane.

[qstong0601]

C3H6 propene It lacks strongly polar bonds, yet the molecule has a small dipole moment due to its reduced symmetry

[macman104]

Yes, it might have a small dipole, but it is still considered nonpolar.  We aren't talking about something that has a zero dipole, but something that would be considered "polar".

Like nj, I'm hesitant to say yes, but I can't think of a good counterexample either.