Write resonance forms that describe the distribution of...

Key Concepts

Resonance

Resonance describes the phenomenon where the actual electron distribution in a molecule or ion is best represented by two or more contributing structures rather than a single Lewis structure. This concept acknowledges that electrons can be arranged in different ways while preserving the overall structure and connectivity of atoms, leading to a more accurate description of the molecule's properties.

Resonance Structures

Resonance structures are individual Lewis diagrams that illustrate alternative placements of electrons (primarily ? electrons and lone pairs) within a molecule. Although these structures do not exist independently, they collectively contribute to the resonance hybrid, which is a weighted average that better represents the true electron distribution.

Formal Charge

Formal charge is a bookkeeping tool used in drawing Lewis structures and resonance forms. It is calculated for each atom to determine the most plausible electron distribution by comparing the number of electrons assigned to the atom in the structure with its number of valence electrons. Stable resonance forms typically minimize formal charges, especially placing negative charges on more electronegative atoms.

Electron Delocalization

Electron delocalization refers to the spreading of electrons over two or more adjacent atoms, rather than being confined to a single bond or atom. This delocalization often leads to increased stability of the molecule or ion, as the energy is distributed over a greater area, allowing resonance stabilization.

Conjugation

Conjugation involves the overlap of p orbitals across adjacent bonds, creating a continuous electron cloud across a segment of a molecule. This interaction is central to the delocalization of electrons in resonance structures, allowing for a lower overall energy and increased stability of the system.

Aromaticity

Aromaticity is a special case of electron delocalization found in cyclic, planar molecules with a conjugated system containing a specific number of ? electrons (following Hückel's rule). This special stabilization is reflected in resonance forms for aromatic compounds, where electron delocalization across the ring is a key component of their unique chemical and physical properties.

Transcript

00:01 Here the question is right resonance forms that describe the distribution of electrons in each of these molecules or ions.

00:13 So, in this resonating structures are present and resonance is possible only when in the molecule or ion, they cannot be represented by just single structure and two or more structures are needed to represent that.

00:32 Particular molecule or ion, then only resonance is present.

00:36 So one by one, we are trying to draw all the structures of the given ion.

00:44 In case of a, the molecule given is sulfur dioxide.

00:58 S -o, sulfur dioxide is given.

01:04 And first of all, we are trying to get the loose structure.

01:08 So in the loose structure, first, all, all the value.

01:11 Electrons so sulfur is 6 valence electrons and oxygen is also 6 so 6 6 12 so total number of valence electrons should be equal to 18 18 valence electron and out of that first central atom we have to find and the central atom here is as one oxygen here, one oxygen here.

01:56 So two bonding pair is used and by that we are using four electrons so minus four and by this total number of 16 electrons left.

02:11 So 16 electron.

02:17 No, it should be 18 minus 4 that means 14 electrons are left so 14 electrons we have to adjust in such a way so that octet is complete.

02:32 So 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 13, 14.

02:46 All the 14 electrons are used.

02:50 But by this oxygen octet is complete but not the sulfur.

02:53 So one electron is forming the bond here.

03:02 So by that if this electron pair is forming the bond here, then the structure should be sulfur with double bond oxygen and here single bond oxygen and one load pair must be here.

03:30 1, 2, 3, 4 is left and 1, 2, 3, 4, 5, 6.

03:40 So this should be one structure.

03:43 And second structure possibly is resonating structures are generally represented by this double arrow.

03:56 And here also you are making the central atom s first and after that single bond this side, oxygen with 8 electrons 6 electrons and here double bond oxygen with 4 electrons and 1 electron pair will be over the sulfur so these are two structures which are possible and by this we are making resonating structure of sulfur dioxide so from this structure if you want to get this structure just this electron pair is shifted here to form the double bond and this electron pair is forming the lone pair and we are getting this structure second structure so these are representing structures of sulphur dioxide now come to b for b structure it is carbonate ion so c o3 2 negative here also first lewis structure and for that carbon is 4 total valence electron 4 plus 18 electron plus 2 negative that means 2 more electron so total number of electron will be 24 24 electron now central atom is carbon and oxygen is forming all oxygen are attached with the central atom by single bond first single bond and after that how electrons left so here for this three single bond six electrons are used and by these total 18 electrons we have to arrange so that the update is complete so we are writing one two three four five six seven eight nine ten eleven twelve thirteen fourteen fifteen sixteen electrons now by this octet of one is complete, this second is also complete but the third octet is not complete and the carbon is also octet is not complete.

06:47 So this should be the structure for making this structure we can arrange like one electron pair we can give to this.

07:03 And by that double bond is formed, formed here and the structure will be carbon, double bond, oxygen, one, two, three, four electrons, 18 electrons, so one electron pair must be here.

07:50 Then one single electron oxygen with eight electrons, six electrons, and one more single bond with oxygen having 1, 2, 3, 4, 5, 6 electrons.

08:10 So this is how this first structure is formed and this is an iron, so it should be kept inside the bracket and it should have minus 2 charge.

08:26 So this is first structure, second structure should be the electron is forming the bond here and this electron is forming the double bond here and by this you are getting the second structure in which one carbon is here second carbon should be second oxygen so here single bond oxygen with six electrons and the octet is complete here it is not disturbed so it will remain same one two three four five six and here double bond is formed with the oxygen and four electrons.

09:24 So here also this structure is the second structure and having minus 2 charge outside and between this we can make the resonating arrow.

09:41 Now next structure in the next structure what happens this electron pair is forming bond here and this electron pair, bonding pair is going to form the electron pair.

09:59 So the third structure should be carbon at the center and double bond should be here with four electrons.

10:21 Single bond will remain same.

10:24 This part is not disturbed.

10:27 Six electron and here one bond is left only with oxygen.

10:32 And 6 electrons, 3 electron low -impairs...

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