Write Lewis structures for each molecule or ion. Use expanded octets as necessary. a. ClF5

Write Lewis structures for each molecule or ion. Use...

Key Concepts

Formal Charge

Formal charge is a tool used to assign charges to individual atoms in a molecule based on the distribution of electrons in the Lewis structure. It is calculated by comparing the number of valence electrons in the isolated atom with the number of electrons assigned to it in the molecule. Minimizing formal charges across a molecule is a common approach to determining the most stable structure.

Expanded Octets

Expanded octets refer to the ability of atoms in the third period or beyond of the periodic table to accommodate more than eight electrons. This happens because these atoms have accessible d orbitals in addition to s and p orbitals, allowing them to form compounds with more than four bonds. This concept is particularly important when drawing Lewis structures for molecules where the central atom forms more than four bonds.

VSEPR Theory

VSEPR (Valence Shell Electron Pair Repulsion) theory is used to predict the three-dimensional geometry of a molecule based on the repulsions between electron pairs around a central atom. This theory helps in understanding and rationalizing the molecular shapes and bond angles seen in various compounds, especially those with lone pairs or expanded octets.

Lewis Structures

Lewis structures are diagrams that show the arrangement of valence electrons in a molecule. They depict bonds between atoms and any lone pairs of electrons, helping to visualize molecular structure, bonding, and reactivity. Drawing Lewis structures involves accounting for each atom's total number of valence electrons and assigning them as bonding or non-bonding electrons.

Octet Rule

The octet rule is a guideline stating that atoms tend to form bonds in such a way that they are surrounded by eight valence electrons, achieving a stable electron configuration similar to that of noble gases. While this rule applies well to many elements, some exceptions occur, especially with elements that can have expanded octets.

Transcript

00:02 All right, to this question, we are asked to draw a number of lewis structures.

00:07 So first up, we have cl5.

00:14 So the first step to solving a lewis structure question is to calculate the number of total valence electrons we have.

00:20 So chlorine has six valence electrons.

00:24 I'm just kidding, guys.

00:26 Chlorine has seven valence electrons.

00:28 Floreen also has seven valence electrons, and we have five of them.

00:36 So in total we have 42, yes, 42 valence of electrons we have to distribute.

00:43 We will start by putting chlorine in the center because it's the least electron negative of the group.

00:49 We'll put five fluorines on there.

00:58 Okay.

01:00 And we just drew five bonds to electrons in each bond.

01:03 So we're going to take away 10 electrons out of our 42 total.

01:07 That leaves us 32 to work with.

01:10 And we will fill in the octets for the fluorines.

01:18 So we'll give each of these fluorines six electrons, and we have five of them.

01:25 So that's 30 of our 32 electrons.

01:29 It means we have two electrons left over.

01:31 We'll put them on the chlorine.

01:33 Now, each of these fluorines has a full octet, so that's fine.

01:39 This chlorine has a total of 12 electrons, which is abloreen.

01:43 Normal, but remember that chlorine is in group three, i mean sorry, in row three or lower.

01:50 So it is allowed to have an expanded octet and have more than, more than eight electrons.

02:01 And one thing we can check just for sanity is the number, is the formal charge.

02:08 So remember that the formal charge is equal to, formal charge is equal to the valence electrons minus the non -bonding electrons minus the number of bonding electrons over two.

02:21 And in this case, chlorine has seven valence electrons.

02:24 It's got zero.

02:26 I'm just kidding.

02:28 It's got two non -bonding, and it's got 10 bonding over two.

02:32 So that's seven minus two minus five.

02:34 That's a formal target of zero.

02:35 So this is our little structure, ladies and gentlemen, for clf5.

02:42 Okay, moving on.

02:46 Next up we have a arsenic and six borings.

02:57 So arsenic is in group 5a.

03:02 It has five valence electrons.

03:06 Thorine is group 7a, so it has seven valence electrons, and there's six of them.

03:15 So that means we have 5 plus 42, that's 48 total valence electrons.

03:23 It's 47 total valence electrons.

03:26 I'm sorry.

03:27 Math is hard for me sometimes.

03:31 Okay, so we put arsenic in the center because it's the least electronegative.

03:36 We will draw six fluorines.

03:46 Oops, i forgot one thing.

03:48 There's a negative charge on this asf6.

03:52 So that means there's actually 48.

03:55 48 valence electrons because this negative charge means there's one of extra electrons so we add that in there.

04:04 Okay, there we go.

04:05 For real, so.

04:07 All right, we just drew six bonds.

04:11 So there's two electrons in each bonds.

04:14 That means we take away 12 of our 48 valence electrons, meaning we have 36 phalance electrons left over to distribute.

04:21 If i put six on each of the fluorines to complete the octets on the fluorines, that means that we have that means we used up our 36 remaining electrons because 6 times 6 is 36.

04:43 So because this is an ion, we have to put brackets around it.

04:51 So we put brackets and we put the minus charge on there.

04:58 Okay, let's move on to our next compound...

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