DAT bootcamp chem q

[panmit]

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Which of the following best describes the bond character for aluminum sulfide (Al2S3)?
A. Polar covalent
B. Covalent
C. Ionic
D. Hydrophobic
E. Hydrogen bonding
Incorrect

Wouldn't this be ionic? I searched it up on google, and I keep on finding that Al2S3 is ionic. Even the chemical name is written as an ionic compound (aluminum sulfide). I get why it could be polar covalent due to the very small electronegativity difference between Al and S. Is there something I'm missing here?

 

[emminent]

That's a good question. I think it's ionic too since it's metal and nonmetal. What did the explanation say?

 

[jwan14]

Yes it would be ionic. It's a mistake

 

[jwan14]

Aluminum is a metalloid isn't it? If I'm wrong maybe that's why...

 

[panmit]

The correct answer is A. Aluminum and sulfur are not very different in electronegativity (1.5 and 2.5, respectively) so the bond cannot be characterized as purely ionic. Their electronegativity is also not close enough to be considered a purely covalent bond. Only pure elements (N2, for example) are purely covalent. Thus, polar covalent is the correct answer.


Aluminum is usually a metal. In very rare instances Aluminum as well as carbon can act as a metalloid.

 

[emminent]

OK so I'm going through my Destroyer for Gchem and one question (question 215 for 2014 version) asked which was most ionic and you could easily narrow it down to Al2O3 or SrF2.

Answer was SrF2 so like you said or like the bootcamp explanation said the further away/different electronegativity two elements are then the more ionic they are. Closer they are then more covalent especially since Al2O3 and Al2S3 are both in the p orbital.