Which of the following substances contains an atom that does not ...

Question

Which of the following substances contains an atom that does not follow the octet rule?
(a) AlCl3 
(b) PCl3 
(c) PCl5
(d) SiCl4

Accepted Answer

Well, everyone's on this video trying to identify the molecules that had an atom that violates the octet rule. So what we can do is just draw all the structures and seeing which one has violated this octet rule. Starting off with our first molecule here as F six. So we have so for being our central atom connected to six fluorine atoms. Alright, now for structure be here, that's AS. F. three. So we have arsenic being r sexual atom here and then it's connected to three florins and we need one long parent. Our central atom here, maybe I'll make them a little bit bigger. All right. And for third structure here O F two, we'll have auction being our central atom connected to two florins here, making two lone pairs necessary for our central atom to fulfill its octet. And lastly we have Model D, which is GEF four. So we have g being our sexual item that's connected to four florins. So taking a look at the central atoms for our last one here or all the items here, we actually have a full octet which didn't draw in the lone pairs for florins. But each flooring will have three lone pairs and we count all the surrounding our electrons. We can see that all items of the structure will have eight electrons which indeed does obey the octet rule. So this one is okay, next one for C. We have the O F two. Again drawn the lone pairs for our flooring animals but it will each have three lone pairs. So if we count all the surrounding electrons, each atom will go ahead and have eight electrons, which does obey the octet rule, C is also safe, and then for B, which is a S. F three again, each flooring does have three lone pairs that are not currently drawn in. And for arsenic in the central item, it does have a electric as well, so all the atoms in this molecule does obey the octet rule. And we see for sulfur here sulfur has six flooring items so that six single bonds, H Singapore and contributes two electrons. So six times two is equal to 12 valence electrons. So the central item does violate the octet rule. So the answer to this question is going to be eight, which is S. F six.

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