Sapling #20

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Gabby Magat 3F
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Sapling #20

Postby Gabby Magat 3F » Sun Nov 29, 2020 10:24 pm

Could someone explain the last part of #20 on the Sapling homework for Weeks 7 and 8? The solution explains that [ AsO4 ]3- is nonpolar due to the symmetry (since it's a tetrahedral shape). If all three of the negatively-charged oxygens are on the "same end" how do they cancel? Wouldn't the dipole vectors point at an angle?

Nick Pascua 2L
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Re: Sapling #20

Postby Nick Pascua 2L » Sun Nov 29, 2020 10:33 pm

Hello,

I believe the charges do not matter when considering dipole vectors. All oxygen atoms will have the same electronegativity value and since it's a tetrahedral, yes they will all cancel out.

Sera Aintablian 2E
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Re: Sapling #20

Postby Sera Aintablian 2E » Mon Nov 30, 2020 1:28 am

Since all three atoms are electronegatively charged and are the same elements, the dipole moments cancel out.

Natalie 3k
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Joined: Wed Sep 30, 2020 10:11 pm

Re: Sapling #20

Postby Natalie 3k » Mon Nov 30, 2020 4:50 am

Hi, I think that because it's the same element with the same electronegativity that's on all the sides, it cancels out. I was kind of confused on whether or not the charges would affect the polarity too but I don't think it does because then it would seem to be polar.

Pranav Daggubati 3C
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Re: Sapling #20

Postby Pranav Daggubati 3C » Mon Nov 30, 2020 9:22 am

The fact that it is an ion doesn't change its polarity. Another thing is resonance in the structure causing even distributions of all forms of [AsO4]3-.

Gabby Magat 3F
Posts: 108
Joined: Wed Sep 30, 2020 10:04 pm

Re: Sapling #20

Postby Gabby Magat 3F » Mon Nov 30, 2020 10:45 am

Nick Pascua 3K wrote:Hello,

I believe the charges do not matter when considering dipole vectors. All oxygen atoms will have the same electronegativity value and since it's a tetrahedral, yes they will all cancel out.


Ohh thank you, this makes more sense now!

Gabby Magat 3F
Posts: 108
Joined: Wed Sep 30, 2020 10:04 pm

Re: Sapling #20

Postby Gabby Magat 3F » Mon Nov 30, 2020 10:45 am

Pranav Daggubati 1A wrote:The fact that it is an ion doesn't change its polarity. Another thing is resonance in the structure causing even distributions of all forms of [AsO4]3-.


Thanks for adding this!

Gabby Magat 3F
Posts: 108
Joined: Wed Sep 30, 2020 10:04 pm

Re: Sapling #20

Postby Gabby Magat 3F » Mon Nov 30, 2020 10:47 am

Natalie 2F wrote:Hi, I think that because it's the same element with the same electronegativity that's on all the sides, it cancels out. I was kind of confused on whether or not the charges would affect the polarity too but I don't think it does because then it would seem to be polar.


Yeah, everyone's explanations help this make more sense--I thought the polar bonds meant the molecule had to be polar, but I guess it comes down to the electronegativity difference/molecular shape.


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