How to determine if covalent compounds are polar?

Question

huhu..

Answer 1

HOJ gave a good answer.In addition one must look to see if there is symmetry in the molecule so that one polar bond would negate another polar bond so the net effect is 0..Example in carbon tetrachloride each C-Cl bond has a net electronegativity differential of 1.3 or so..BUT the molecule is symmetrical about the C atom

                                      

so the net dipole moment is zero since each bond pulls back the electrons from the other oppsosite it

Answer 2

to determine whether a covalent cmpd is polar or non- polar you just have to subtract the individual electronegativity of atoms. for example HCl, Cl has electronegativity value of 3.0 and H has 2.1. The difference would be 0.9 and there is a dipole moment which means it is polar. The cmpd is non- polar if the difference is 0. An example is hydrogen gas, both H have 2.1 values and subtracting them would give you zero and thus no dipole moment.