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"Use your knowledge of bonding to fully explain (without using diagrams) what the...

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alihumbo | eNotes Newbie

Posted March 25, 2013 at 6:12 PM via web

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"Use your knowledge of bonding to fully explain (without using diagrams) what the molecular formula and structure of the compound containing aluminium and sulfur is"

I have science homework due in tomorrow and I haven't got a clue on what it's about... Does anyone know the answer to this question they're asking me?  

I haven't got a clue, but anyone that is willing to help, I would be really grateful :)

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ncchemist | eNotes Employee

Posted March 26, 2013 at 11:20 PM (Answer #2)

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Let's look at both Al and S on the periodic table.  Their positions on the table will tell us what we need to know.  Aluminum (Al) is in group 13.  This means that it has three valence electrons, or electrons in its outermost energy shell.  So Al can lose these three electrons to become the Al^3+ cation (three is the maximum number of electrons that can normally be lost to make an ion).  Losing these three electrons will give it an octet of electrons in its new valence shell (8 valence electrons is the magic number for stability).  Sulfur (S) is in group 16.  This means that it has 6 valence electrons.  If it were to gain two more electrons it would have an octet.  So S can become the S^2- anion.

So if we have Al^3+ and S^2- ions we need to find a way to combine them to make a neutral compound.  If we have 2 aluminums and 3 sulfurs, that would give us a total of 6 positive charges and 6 negative charges which would balance out to a neutral compound (a net charge of 0).  So aluminum and sulfur combine to make aluminum sulfide, or Al2S3, an ionic solid.

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