#37 on Chapter 3

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Ashley Davis 1I
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Joined: Fri Sep 29, 2017 7:04 am

#37 on Chapter 3

Postby Ashley Davis 1I » Thu Nov 02, 2017 2:40 pm

Could someone explain how to do this problem. Like how would we know which Period 3 element it would be...

Nisarg Shah 1C
Posts: 54
Joined: Sat Jul 22, 2017 3:00 am

Re: #37 on Chapter 3

Postby Nisarg Shah 1C » Thu Nov 02, 2017 2:50 pm

Because the element is in Period 3 and has an expanded octet, you can deduce it will most probably be Silicon, Phosphorus, Sulfur or Chlorine. The other elements in Period 3 are more likely to form ionic bonds (Na and Mg), do not have an expanded octet (Al), or are not common in bonding reactions (Ar). By calculating the formal charge of the central atom of each of the above elements, you can find that Phosphorus is the only element with a formal charge of 0.

Nisarg Shah 1C
Posts: 54
Joined: Sat Jul 22, 2017 3:00 am

Re: #37 on Chapter 3

Postby Nisarg Shah 1C » Sun Nov 05, 2017 9:47 pm

Alternatively, an easier method is to calculate the total number of electrons in the Lewis Structure. And then subtract the valence electrons of every known element, to find the mystery element's valence electrons (which should be 5). And Phosphorus is the only element in Period 3 with 5 valence electrons!


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