Can nonpolar molecules have polar bonds?

Answer 1

Sometimes, there can be.

If there is, it must all cancel out. If you consider #"CO"_2#, we know that's nonpolar linear:

#:stackrel(..)"O"="C"=stackrel(..)"O":#

but we should note that it has two dipole moment vectors in the #z# direction:

#stackrel(larr)( :stackrel(..)"O"=)"C"stackrel(rarr)(=stackrel(..)"O": )#

These are of equal magnitude but opposite direction, so they cancel out perfectly. Thus, #"CO"_2# is considered nonpolar.

However, it doesn't mean #"CO"_2# can't be polarized, which is another story. It has two infrared bands near #"2360 cm"^(-1)#.

These correspond to #"CO"_2#'s asymmetrical stretching and bending vibrational modes. It has two nondegenerate modes that are IR-active as shown below:

If it were not possible for #"CO"_2# to develop a net nonzero dipole moment (thereby changing its dipole moment, one prerequisite for an IR band, the other being the asymmetry of the vibrational mode), we wouldn't see these infrared bands.


We could have treated these identical-magnitude dipole moment vectors as #vecl = << 0,0, 1 >># and #vecr = << 0,0,-1 >>#. In that case, we can show that they cancel upon summing them together:

#vecl + vecr#

#= << 0,0,1 >> + << 0,0,-1 >>#

#= << 0,0,0 >> = vec0#

which is a dot, representing the nonpolar result of two dipole moment vectors of identical magnitude and perfectly opposite directions summing together.

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Answer 2

Yes, nonpolar molecules can have polar bonds if the polarities of the bonds cancel each other out due to symmetry or the arrangement of atoms.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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