Lewis Dot Structures: Neutral Compounds (Simplified) - Online Tutor, Practice Problems & Exam Prep

Lewis Dot Structures: Neutral Compounds (Simplified) Concept 1

Now Lewis dot structures are structural representations of elements that use valence electrons to form their covalent bonds. We're going to say that there are many possible Lewis bond structures that exist, but there are rules to draw the best structure. Recall, elements form bonds in order to gain electrons and become like the nearest noble gas. So when we're drawing these Lewis dot structures, we're going to go through a series of rules that help us to illustrate the best connections for those particular Lewis dot structures, also known as molecular compounds.

Lewis Dot Structures: Neutral Compounds (Simplified) Example 1

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.

Determine the Lewis Dot Structure for the NH₃ compound.

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Determine the Lewis Dot Structure for the following compound:H₂Se.

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Draw a Lewis Dot Structure that obeys the octet rule for the following compound:NH₂OH.

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