most polar molecular compound

[joonkimdds]

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choices are
a. BF3
b. CF4
c. CBr4
d. CH2Cl2
e. CH2Br2

I understand that a,b,c will have no net dipole moment because they will cancel each other.

But I am not sure about the choice D and E.
the solution says D is the answer because Cl is more electronegative than Br.

I think answer should be E because
C is more electronagative than Br and Cl so electrons from
both Br and Cl will be pulled by C.
the difference in electronegativity of C-Br is greater than C-Cl
so shouldn't C-Br be more polar? Cl is more electronegative than Br
so it will have more resistance against C pulling electrons around it.

By the way, is H more polar than C?
and is it true that C is more electronegative than Br and Cl like i said?
I assume that it's true because C is closer to the nucleus.

 

[andyjl]

C-Cl is more polar than C-Br because, like you said, Cl is more electronegative, therefore the difference in electronegativity between the Cl and C will be much greater than C-Br. The Cl atom has a greater tendency to pull electron density toward itself. Remember electronegativity increases going up the periodic table.

As far as H being more polar than C; I think you are asking the wrong question about that, because H and C are atoms so they are just considered neutral atoms, it is when they are bonded to another atom is when you consider polarity. C-H bonds are not neutral, but slightly polar, and I believe, that the partial negative charge is on the Hydrogen atom.

 

[joonkimdds]

C-Cl is more polar than C-Br because, like you said, Cl is more electronegative, therefore the difference in electronegativity between the Cl and C will be much greater than C-Br. The Cl atom has a greater tendency to pull electron density toward itself. Remember electronegativity increases going up the periodic table.

As far as H being more polar than C; I think you are asking the wrong question about that, because H and C are atoms so they are just considered neutral atoms, it is when they are bonded to another atom is when you consider polarity. C-H bonds are not neutral, but slightly polar, and I believe, that the partial negative charge is on the Hydrogen atom.

Since C has the largest electronegativity, and then Cl and then Br,
I could say C=3, Cl=2, Br=1.
The difference between 3 and 1 is bigger than 3 and 2 so shouldn't
C and Br have bigger polarity?

oh and i made typo about asking H being more polar, i meant to say H is more electronegative than C 🙂

 

[Lonely Sol]

C-Cl is more polar than C-Br because, like you said, Cl is more electronegative, therefore the difference in electronegativity between the Cl and C will be much greater than C-Br. The Cl atom has a greater tendency to pull electron density toward itself. Remember electronegativity increases going up the periodic table.

As far as H being more polar than C; I think you are asking the wrong question about that, because H and C are atoms so they are just considered neutral atoms, it is when they are bonded to another atom is when you consider polarity. C-H bonds are not neutral, but slightly polar, and I believe, that the partial negative charge is on the Hydrogen atom.

No, the C-H bonds are nonpolar bonds, just think of an n-alkane, the longer the chain gets (more C-H bonds) the more non-polar it is. For example, hexane is more non-polar than pentane.

Also, The partial negetive is on the carbon and partial positive on the hydrogen atom.

 

[Dotoday]

Hi, the answer is "D" , I just looked it up. I am positive.

 

[joonkimdds]

No, the C-H bonds are nonpolar bonds, just think of an n-alkane, the longer the chain gets (more C-H bonds) the more non-polar it is. For example, hexane is more non-polar than pentane.

Also, The partial negetive is on the carbon and partial positive on the hydrogen atom.

oh, ok. so i guess Carbon is more electronegative than H even though it's farthur away from the nucleus?
what about Carbon - Cl ? which one has partial negative?
I believe carbon has higher electronegativity?

 

[Lonely Sol]

oh, ok. so i guess Carbon is more electronegative than H even though it's farthur away from the nucleus?
what about Carbon - Cl ? which one has partial negative?
I believe carbon has higher electronegativity?

No, Cl has the partial negetive because Cl is higher in electronegetivity and C has the partial positive charge (know your trends, very crucial)!!