Write Lewis structures that obey the octet rule (duet rule for H ) for each of the following mol

Write Lewis structures that obey the octet rule (duet rule...

Key Concepts

Bonding and Multiple Bonds

Bonding electrons in Lewis structures can be arranged as single, double, or triple bonds. Multiple bonds, such as double or triple bonds, are often necessary to satisfy the octet rule for atoms that do not achieve eight electrons through single bonds alone. This concept is essential in constructing structures where some atoms need additional electron density to reach a stable configuration.

Formal Charge

Formal charge is a bookkeeping tool used to assign a charge to individual atoms in a molecule, assuming equal sharing of bonding electrons. Calculating formal charges helps in determining the most plausible Lewis structure among several possibilities, ensuring that the structure has minimal formal charges and that any charges are localized on atoms that can best accommodate them.

Central Atom Selection

In drawing molecular structures, the central atom is typically the one with the lowest electronegativity (except hydrogen) as it can accommodate multiple bonds and lone pairs. Selecting the correct central atom is crucial for correctly depicting the molecular structure in a way that reflects the connectivity and electron distribution.

Octet Rule

The octet rule states that atoms (usually main-group elements) tend to form bonds until they are surrounded by eight electrons in their valence shell. This rule is used as a guideline to determine how atoms can bond and achieve a more stable electron configuration in a molecule.

Lewis Structure

A Lewis structure is a diagram that represents the valence electrons of atoms within a molecule. It shows how these electrons are arranged between atoms in the form of bonds (shared pairs) or as lone pairs, providing a visual method to understand the molecule’s geometry and reactivity.

Duet Rule

The duet rule applies primarily to hydrogen. It indicates that hydrogen is most stable when it has two electrons in its valence shell, resembling the electron configuration of helium. When drawing Lewis structures, hydrogen should be connected in a way that it only shares two electrons.

Transcript

00:02 Okay, we're going to be looking at lewis structures and using the lewis structure in these two rules of the octet rule and the duet rule to kind of draw some different lewis structures of some different molecules.

00:15 And so let's look at some different molecules here.

00:18 One of them that we could look at is this one right here, a very common molecule, so h2co.

00:27 And kind of how we do this, we want to follow these different steps, specific steps.

00:31 The first step that we want to do is count how many valence electrons there are.

00:35 And do that, we would need to have the periodic table, look and see where they're at on the periodic table and determine.

00:41 Hydrogen, since it's in that first group, we know that it's going to have one extra valence electron.

00:48 It's going to have one electron in its outer shell, one valence electron.

00:53 So we're going to add these all up.

00:54 And we have two hydrogen.

00:57 So i'm going to add those right there, so one plus one.

00:59 Carbon is over there in the periodic table if i was to draw it out kind of like so it is right here in that second column it has four extra electrons and it's outer shell and you could really solve these doing your like 1s1 to you know filling out those orbitals but you can just look at the periodic table as well the first group right here would have ones, would have two.

01:32 These transitional metals are kind of a little iffy.

01:35 You can't use that model.

01:37 But then over here you'd have three, four, five, six, seven, and then eight valence electrons are always found in your noble gases.

01:46 And so ultimately we want all these atoms to follow the octet rule, meaning that they have a noble gas kind of happiness level in their configuration.

02:00 So we have 1 plus 1 plus 4.

02:03 Oxygen is in the seventh, or a 6 column, the 16th, i guess, if you wanted to count them over, but 16th.

02:10 So therefore it has 6 over there.

02:12 Okay, so 6 plus 4 plus 1 plus 1.

02:15 If we had that all up, that equals 12 electrons that we need to put in this structure.

02:25 So i always like to start out with these ones.

02:27 So carbon bonds to oxygen, we've then used one right there.

02:30 And then we have two hydrogen that are going to be put somewhere in here.

02:34 I don't know where yet, though.

02:37 And, well, we do know it bonds to carbon because it's found over here.

02:40 If not, it would be over here.

02:42 And so i'm just going to draw that as this, for example, where we have two hydrogen.

02:50 So we have one, two, three, four, five, six.

02:52 So we've then used six electrons already, leaving us with six that we need to put somewhere in here.

02:59 Let's just start filling out.

03:03 The molecules right here.

03:05 Okay, so right there.

03:06 We've got our six.

03:07 I've just added them there.

03:08 Each point is referring to an electron according to in this lewis structure.

03:14 Now let's just see and make sure it follows these two rules.

03:16 So the duet rule only applies to hydrogen, which we have two of them here.

03:21 And basically it says that hydrogen needs to have two electrons.

03:25 So one, two, one, two.

03:28 So we're good.

03:29 Carbon and oxygen need to follow the octet rule, meaning that they have eight electrons.

03:34 So carbon has one, two, three, four, five, six.

03:37 So it's not following the octet rule.

03:39 So we've got to do some little bit more work there.

03:41 Let's see if oxygen's falling in.

03:42 So we have one, two, three, four, five, six, seven, eight.

03:45 Okay, so we have oxygen having eight, carbon having six, and there.

03:49 So right here we have a little issue.

03:51 We need to give it two more electrons somehow.

03:54 And so what we would do is we would want to bring these right there and make a double bond.

04:01 So let's redraw this.

04:03 So we have carbon.

04:11 And so.

04:12 Now let's see if it still follows it.

04:14 So we have our hydrogens.

04:15 Hydrogen is still carrying two.

04:17 Carbon.

04:17 One, two, three, four, five, six, seven, eight.

04:19 Yeah, it's better.

04:21 Let's make sure oxygen's good.

04:22 One, two, three, four, five, six, seven, eight.

04:25 So there we go...

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