Write Lewis structures for each molecule or ion. Use expanded octets as necessary. a. PF5

Video transcript

Hello everyone today. We're being asked to draw a plausible lewis dot structure for sulfur trioxide. This structure might have an expanded octet. The first thing we wanna do is we want to take into account how many electrons we are working with. So in this sulfur trioxide we have one sulfur and we have three oxygen's. So we have one sulfur and sulfur is in the sixth group on the periodic table and therefore has six valence electrons, giving us a total of six electrons here. And for oxygen we have three of them. And oxygen is also in the sixth group on the periodic table and therefore has six valence electrons as well, giving us 18 electrons to work with. This whole number of electrons therefore is going to equal to electrons. And so the second they're going to do is they want to identify the least electro negative atom because the least electro negative atom goes in the center. So we say that it goes in center. And so according to the periodic trend, the electro negativity increases as we go to the right and up on the periodic table. Therefore sulfur is going to be in the center as it has a lesser electro negativity. We're gonna connect this sulfur with the three oxygen's present notice how we've used three bond lines and each bond line has two electrons. And so therefore we've used six electrons. So we're gonna take our 24 electrons and we're going to subtract six, Giving us 18 electrons left to work with. The next thing we're gonna do is we want to draw our Electrons around the outer elements or atoms to fulfill not only the architect rule but their valence electron rule as well. So oxygen is in group six. And so it should have six valence electrons around it. And so what we're gonna do We're going to draw 12345. But notice how we have an unpaid electron. So this can't be correct and this is going to be true for all of the oxygen as well as they're all equivalent. So what we need to do is we need to draw another bond line that somehow connects the cell furs as such with the oxygen's. Now remember Sulfur is a group six electronic adam as well And therefore we'll have six valence electrons as we see here. 123456. Notice something interesting about it though. It has a total of six bonds to it. And so we always learned that atoms can only have an octet rule which means that they can only have a electrons surrounding it. However, sulfur isn't special rule because it is A is in the third period And the 3rd period Adams can have an expanded octet. So since we have used six more electrons we must take that into account. So we only have 12 left. What we're gonna do is we're gonna try and fulfill the architect role with oxygen. And so to do that we just simply need to draw four electrons around each remaining oxygen, And we have used up our 12 remaining electrons and have our final lewis dot structure for sulfur trioxide. I hope this helped, and until next time.