March 26, 2017

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"Is the following species a dipole?"

I have drawn out the lewis dot structure of the molecule and the electronegativy values I have are
N- 3.0
Cl- 3.0
H- 2.1

I know that the electronegativity difference between N and Cl is 0 and the bond is non polar. In my structure, I have this:
with N being bonded to Cl as well and having a free electron pair. Since both hydrogens are being pulled into N with the same "force" or "attraction" is there still a dipole?

Sorry that my question was confusing

Your description of the bonding is a little confusing but I THINK you have it right. I will summarize here just to make sure.
N is the central atom. It has an unshared pair of electrons. A pair of electrons is shared with each H atom and the Cl atom. That makes 3 shared pairs plus an unshared pair which makes four regions of high electron density and that means a tetrahedral arrangement. So a pair of electrons is at one apex, A Cl atom at another and a H atom at the other two "corners." So it is not symmetrical. If there is ANY difference of electronegativity AND the arrangement is not symmetrical (this one isn't), there is a dipole moment. The NH4+ is symmetrical; therefore, even though H and N don't have the same EN, the symmetry of the ion cancels and there is no dipole moment.

Ok, thank you that clears it up a bit =]
I have another question. If I have the ion, NO3-, and I know that it's a resonance structure with one double bond and two single bonds, is this still non-polar? Or does the double bond affect the polarity?

The double bond doesn't change the polarity. The N is the central atom, with no unshared pairs of electrons. It shares two pair with one O, and a pair with each of the other O atoms. At least that is one resonance structure we can draw. So it has three regions of high electron density (one to double bond O and one each to the other two O atoms). Three regions of high electron density is trigonal planar and that is a symmetrical structure. That gives us N in the center and O at the three corners. So no dipole.

  • Chemistry - ,

    I confirm your answer :)

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