Draw Lewis structures for (a) AsH3, (b) HClO2, (c) H2 SeO3, and (𝐝) H3 AsO4.

Name: Problem 94, Chapter 9: Chemistry The Molecular Nature of Matter
Uploaded: 2021-12-12T17:56:02-08:00
Duration: 7 min 57 s
Channel: Crystal Wang
Description: Draw Lewis structures for (a) AsH3, (b) HClO2, (c) H2 SeO3, and (𝐝) H3 AsO4.

step 1 So we're going to draw blue structures for the given compounds. So our first step is to calculat

Draw Lewis structures for (a) AsH3, (b) HClO2, (c) H2 SeO3,...

Key Concepts

Formal Charge

Formal charge is a tool used to evaluate the electron distribution within a molecule by assigning charges to atoms based on an assumed equal sharing of electrons in chemical bonds. It helps in determining the most likely Lewis structure among several possibilities by minimizing charge separation, with structures exhibiting the lowest formal charges generally being the most stable.

Expanded Octet

An expanded octet occurs when atoms, typically from the third period onward, accommodate more than eight electrons in their valence shell by utilizing available d-orbitals. This concept is essential when drawing Lewis structures for molecules where central atoms are capable of forming additional bonds, allowing for a stable structure with an electron count that exceeds the octet rule.

Bonding Patterns

Bonding patterns refer to the typical ways in which atoms bond, including the formation of single, double, or triple bonds. Recognizing these patterns is key to predicting molecular geometry, polarity, and reactivity. Understanding how atoms share electron pairs to achieve complete electron shells is essential when constructing accurate Lewis structures.

Valence Electrons

Valence electrons are the electrons present in the outermost shell of an atom that are available for bonding. The total number of these electrons determines how atoms bond with each other, the structure of the molecule, and the arrangement of electrons in Lewis structures. Calculating the sum of valence electrons for all atoms in a molecule is the first step in drawing an accurate Lewis structure.

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. These structures help visualize the electron pair distribution and provide a simplified model of the molecule’s three-dimensional arrangement. They are crucial for understanding how atoms interact and bond with one another in chemical compounds.

Octet Rule

The octet rule is a chemical guideline that states atoms tend to form bonds in such a way that they have eight electrons in their valence shell, achieving a noble gas electron configuration. This rule is a foundational concept in constructing Lewis structures, although it does have exceptions, especially for atoms in the third period and beyond.

Transcript

00:01 So we're going to draw blue structures for the given compounds.

00:07 So our first step is to calculate the number of valence electrons.

00:12 So let's find arsenic on the periodic table.

00:17 It is in group 15, so that means that it contributes five valence electrons.

00:25 Then we have three hydrogens.

00:28 Each of those will contribute three.

00:30 We therefore have eight total electrons.

00:33 So we know arsenic has to be the center because hydrogen can only form one bond.

00:41 And we have eight electrons.

00:44 So therefore, we have to put two onto the arsenic to have a have the octet.

00:49 And then we can't really form any double bonds.

00:54 So this is just going to be the loose structure.

00:57 So let's do b.

01:03 Okay, so now start with advanced electrons from hydrogen, chlorine, and oxygen.

01:14 So we get 20 total.

01:23 So in this case, it looks like chlorine and oxygen are both going to end up kind of being in the center.

01:43 So basically, we'll have the hydrogen bonded here, and we'll have oxygen bonded here, and we'll have the hydrogen bonded to the oxygen.

02:05 It's going to look like that.

02:13 So now we have eight here.

02:19 Eight plus four is 12 electrons.

02:22 Topal deus 20.

02:23 So we satisfy the number of electrons, but we know that the formal charges on the oxygen are going to be minimized if we form double bonds.

02:32 We want to form double bond to the oxygen if we can.

02:37 So we should be able to do that because there's no restrictions.

02:43 We do have some electrons on chlorine that we can use.

02:47 Form the double bond.

02:53 Okay, and then when we have an oh group, we can't really form a double bond to the oh group because we have the oxygen sharing a pair of electrons with hydrogen.

03:06 So we cannot form a double bond to an oxygen that's already sharing one of the electron pairs with the hydrogen.

03:15 So we don't really have to do anything else then.

03:19 This becomes, well, let's count the ox, or count the electrons to make sure that we have enough of them.

03:47 So it looks like we actually are missing two electrons...

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