A series of anions is shown below:
The anion on the far right is called 'BARF' by chemists, as its common abbreviation sounds similar to this word. (b) What is the electron-domain geometry around the central B in BARF?

Question

A series of anions is shown below:

The anion on the far right is called 'BARF' by chemists, as its common abbreviation sounds similar to this word. (b) What is the electron-domain geometry around the central B in BARF?

Accepted Answer

welcome back everyone in this example, we need to determine the compound with the expanded octet surrounding its central atom. From the following molecules below. So we need to recall that to have an expanded octet. We must be a period three or below element as the central atom. And recall that having an expanded octet means you can violate the octet rule which is to have eight electrons around yourself in the lewis structure. So beginning with choice A. We can see that sulfur is our central atom. Recall that on our periodic table sulfur we can find in group six A. Sorry, that's group six A. And it lies across period three. So it should be able to violate the octet rule and have an expanded octet. But right now we can see that we have two bonds of our sulfur to these two carbon atoms here recall that each bond contains a total of two electrons. So we would count to four electrons so far. And then we have these two lone pairs on our sulfur atom where we would count six and then 78 electrons around sulfur. So we can see that sulfur here does not violate the octet rule. So it does not have an expanded octet even though it is capable of having one, It does not in this example. And so we would rule out choice A. And move onto Choice B. And Choice B. We can see that phosphorus is our central atom recall that phosphorus on our periodic table is located in group five A. And also lies across period three. So it should be able to violate the octet rule and have an expanded octet right now we see three bonds of phosphorus to carbon. Where each bond we recall contains a total of two electrons, so we would count six electrons. And then we see that we have this lone pair on phosphorus accounting for our last two electrons to give us a total of eight around this phosphorus atom, meaning it honors the octet rule in this case and does not have an expanded octet even though phosphorus is capable of doing so because it's a period three elements, we would rule out choice B. Choice C. We can see has nitrogen as the central atom. So recall on our periodic table that nitrogen is located in Group five A. Across period three, meaning it should be able to violate the octet rule. So we would count a total of three carbon atoms bonded to our central nitrogen atom in three bonds where each of these three bonds represent a total of six electrons. And we also have one lone pair on the nitrogen atom. So we have the same pattern as phosphorus in our previous molecule. So here we can see nitrogen also does not have an expanded octet, meaning we would rule out choice C. And our only correct answer is going to be choice D. That none of the above molecules have shown us that they can have an expanded octet on their central atom. So d is our final answer. I hope everything I reviewed was clear. If you have any questions, leave them down below and I'll see everyone in the next practice video.

A series of anions is shown below: The anion on the far right is called 'BARF' by chemists, as its common abbreviation sounds similar to this word. (c) Which, if any, of these anions has an expanded octet around its central atom?

Verified Solution

Key Concepts

Expanded Octet

Central Atom in Anions

Lewis Structures