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Hannah Chew 2A
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Postby Hannah Chew 2A » Thu Nov 16, 2017 8:56 pm

Can anyone explain why SiO2 is polar without knowing what the electronegativity values are? This topic was in another forum, but I'm still confused. Dr. Lavelle specifically said in class that we will not need to know the electronegativity values and that we can determine the difference in electronegativity based on location on the periodic table. With that being said, how do we determine if SiO2 is polar? Si and O are very close on the periodic table, and the net dipole moment of SiO2 is 0 since the shape is linear... any help is appreciated!

Curtis Tam 1J
Posts: 105
Joined: Thu Jul 13, 2017 3:00 am

Re: SiO2

Postby Curtis Tam 1J » Thu Nov 16, 2017 8:59 pm

Lol got the same question wrong on the midterm if that's what you're asking about. The bonds themselves are polar. The molecular overall however is nonpolar. Since the test was covering chapters 1 through 3, you shouldn't have used the idea that dipoles can cancel each other out. That was taught in chapter 4. In chapter 3, we merely said that anytime there's an EN difference, there is more ionic character and therefore greater polarity. I put nonpolar too lmao.

Minie 1G
Posts: 63
Joined: Fri Sep 29, 2017 7:04 am

Re: SiO2

Postby Minie 1G » Thu Nov 16, 2017 9:16 pm

You know that the Si-O bonds are polar because of their location on the periodic table. We know that C-O bonds are polar, since oxygen is more electronegative than carbon, and Silicon is in the same group as carbon -> Si-O bonds are also expected to be polar.

Isaiah Little 1A 14B
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Joined: Fri Sep 29, 2017 7:05 am

Re: SiO2

Postby Isaiah Little 1A 14B » Thu Nov 16, 2017 10:45 pm

SiO2 is polar based on the electronegativity differences between Silicon and Oxygen, which can be interpreted from the periodic table. Although the SiO2 molecule itself is non-polar due to symmetry, the bonds between the Si and O atoms are polar.

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Re: SiO2

Postby AtreyiMitra2L » Sat Nov 25, 2017 12:46 pm

If you read the q, it asks for the bond type. So while the molecule itself may be non polar, the two bonds within are polar. O is more electrons than Si. Therefore, it will pull the electrons more than Si. This will create two polar bonds.

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