Here it says we need to draw the Lewis dot structure for the silicon tetrabromide molecule, which is SiBr4. To do that, we're going to take a look at the following rules. Alright. So step 1 says that we need to determine the total number of valence electrons of the structure. Now recall, the total number of valence electrons equals the group number of the element. So here we have silicon, which is in group 4A, and there's one of it. And then here we're going to say we have bromines. Bromines are in group 7A, so there are 7 valence electrons each and there are 4 of them. So 28 +4 gives me 32 total valence electrons within this structure. Alright.
Step 2, we're going to place the least electronegative element in the center and connect all elements with single bonds. Alright. So we're going to say silicon is less electronegative than bromine. So we're going to connect silicon to the 4 bromines. Now remember silicon is in group 4 so it contributes 4 valence electrons here. And remember each single bond has in it 2 valence electrons. So here goes the other electron on the other end. Alright. To do this, remember, we're going to follow the bonding preferences guide to determine atom connectivity. We know this makes sense because silicon is in group 4A, elements in group 4A want to make 4 bonds.
Step 3, we're going to add electrons to all surrounding elements until they have 8 electrons, which we refer to as the octet rule. But remember, we also have the duet rule when it comes to hydrogen. Hydrogen only wants 2 valence electrons around it because doing so gets us the same configuration as helium. Right. Now, we're going to add all the electrons that we can. So we've already used 8 electrons. Right? So that means that we have what? 24 electrons remaining. So 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24. So we've used all 24 remaining electrons, so we have 0 left. So, step 4 you don't have to do. Step 4 says we place any remaining electrons on the central atom. In this case, we don't have any electrons remaining and this would be our structure. We'd have silicon making 4 bonds, it would have 0 lone pairs on it, each bromine is making a single bond, and each one has 3 lone pairs on it. So this would be the structure for our silicon tetrabromide molecule.
