in BCl3 the resultant of dipole moments of two B-Cl bonds is opposite to the dipole mom. of a single B-Cl bond

Question

then how can they cancel out each other.......as the magnitude of resultant of two dipole moments of B-Cl bond will not be equal to the dipole mom. of the single B-Cl bond.??????????

Answer 1

You need to treat them as vectors. Remember that vectors have a magnitude and direction. So, since all three B-Cl bonds are 120 ˚ apart from each other, so adding any two, taking into consideration the angle between them, will give you a vector that has the same magnitude and opposite direction of the other vector in the molecule. So, they do cancel each other out perfectly, making boron trichloride a nonpolar molecule. Refresh your geometry and you see that what I explained is true. Use graph paper to see it clearly.

Answer 2

They all cancel out, because they are at 120 degrees to each other. Take any one bond, and you have two others opposite it, but pulling away from the B-Cl line by 60 degrees either side.

Answer 3

atom B have 5 electrons valence. and need 3 electrons for same with inert gass. and Cl have 7 electrons valence and need 1 electron for same with inert gass. B and 3 atoms Cl can reacting for same with inert gass
and bond B-Cl single is covalent bond.