Midterm

[leilawilliams16]

What were the correct answers for the bond identifications (ionic, non polar, polar) on the midterm? I believe one molecule was KCl and another was N2 but I forget the third.

[Cynthia Tsang]

I think it was SO2. KCl was ionic. SO2 was polar and N2 was nonpolar.

[804899546]

It was actually SiO2, but nevertheless it is still polar, as the difference in electronegativity was greater than 1.5.

[Kayla Ikemiya 1E]

I got:
KCl is ionic
N2 is non polar because the structure equally shares the electrons because the same element has the same electronegativity value
SiO2 is polar

[Eryn Wilkinson 3H]

How do you know that SiO2 is polar if you don't know the specific electronegativity difference? The elements seem fairly close together on the periodic table, and since there are two oxygens wouldn't the dipole moments cancel?

[Courtney Cheney 3E]

I'm confused because Silicon has 4 ve- while both Oxygen's have 6 ve- which add up to a total of 16 ve-. So when you draw the Lewis Structure, you're going to get Silicon double bonded to each Oxygen atom and 2 sets of lone pairs on each Oxygen.
(The two double bonds makeup 8e- while the 2 set of lone pairs on each oxygen make up the remaining 8e-)
Since there are no lone pairs on Silicon, the shape is linear so wont the dipole moments of Oxygen cancel out and make the molecule nonpolar?

[Courtney Cheney 3E]

I believe that the difference in electronegativity guideline(the <1.5 or >2) only works to determine if the molecule is an ionic bond or covalent bond. And then you have to figure out the shape and dipole moments to determine polarity