Draw as many resonance structures as you can that obey the octet rule for each of the following

Draw as many resonance structures as you can that obey the...

Key Concepts

Resonance Structures

Resonance structures are multiple valid Lewis structures for a single molecule that depict delocalized electrons in different positions. They are used to represent the true electronic structure of a molecule when a single Lewis formula cannot accurately describe its bonding. Resonance forms illustrate the idea that the actual electron distribution is a weighted average (or hybrid) of the individual structures, which can help in understanding properties like charge distribution and reactivity.

Octet Rule

The octet rule is a guideline used in constructing valid Lewis structures, which states that atoms tend to form bonds until they are surrounded by eight valence electrons. This rule is especially applicable for second period elements and is used to determine whether a resonance structure obeys the preferred electron configuration. When drawing resonance structures, ensuring that atoms satisfy the octet rule (or the expanded octet in certain elements) helps maintain stability in the theoretical representation.

Formal Charge

Formal charge is a bookkeeping tool used to determine the charge distribution within a molecule as represented by a Lewis structure. It helps in assessing the relative stability of different resonance forms; structures with minimal formal charges, or with negative charges localized on more electronegative atoms, are typically more stable. When drawing resonance structures, calculating formal charges on atoms ensures that the most stable and representative forms are identified.

Lewis Structures

Lewis structures offer a simplified representation of a molecule’s electron configuration by showing how valence electrons are arranged among atoms in bonds and as lone pairs. They serve as the starting point for constructing resonance forms, aiding in the visualization of electron delocalization and adherence to the octet rule. Mastery of drawing Lewis structures is essential for understanding molecular geometry, reactivity, and the overall behavior of molecules.

Transcript

00:01 For this question, you're simply asked to draw as many resonant structures that obey the octet rule for the following molecules or ions.

00:08 First one is hn3.

00:10 Hydrogen has one valence electron and has five.

00:13 There are three of them, so we have a total of 16 valence electrons.

00:16 So let's put all three nitrogen in a row and then add the hydrogen on the end.

00:21 That's used up six, so we have ten left over.

00:27 So we could end up double bonding the nitrogen's.

00:30 That then uses up four more, so we have six left over.

00:34 One, two, three, four, five, six.

00:38 Now while the nitrogen have an octet, and the hydrogen has a duet, so we're good.

00:44 If we could have put a double bond here and a double bond here, there's no reason why we couldn't have put a trip bond between two of the nitrogen's, say on the left -hand side or the two nitrogen on the right hand side.

00:58 Next one is sulfur trioxide, dioxide.

01:00 Sulfur has six valence electrons.

01:02 Oxygen has six.

01:03 There are three of them.

01:04 So we have 24.

01:06 If we put sulfur in the middle, we put three oxygens around it, we've used up six of the 24.

01:11 So we have 18 left over.

01:13 Two, four, six, eight, ten, twelve, fourteen, sixteen, eighteen.

01:20 All the oxygens are good, but the sulfur only has six valence electrons...