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consider this molecule

what are the bond orders for each Bond

shown in this diagram

so let's start with the CH Bond what is

the bond order

for bonds that are not involved in

resonance

the bond basically tells you the bond

order

so for a single Bond the bond order is

one

for double bond the bond order is two

and for a triple bond the bond order is

3.

now for bonds that are involved in

resonance you can have fractional Bond

orders

so for the CH Bond that's simply a

single Bond so that's going to have a

bond order of one

every

single bond that we see here

that doesn't participate in resonance

has a bond order of one

the double bond has a bond order of two

the triple bond has a bond order of

three

now let's focus on this group right here

I'm going to redraw it like this

and let's show the lone pairs

so we have two lone pairs on the

carbonyl oxygen three lone pairs on the

other one

now

if there were no resonance structures

you'd assume that this would have a bond

order of two

but because we can draw

a resonance structure

the bond order is going to be different

if we take a lump here

we can use it to form a pi Bond and we

can break this Pi Bond put in two

electrons on that oxygen

so this oxygen will now have two the

other one will have 3 and the negative

charge

so now looking at this particular Bond

would you still say it has a bond order

of two

because here it looks like it has a bond

order of one

it turns out that the the actual answer

is going to be an average of those two

numbers it's 1.5

so the way you would calculate bond

order

is you would look at the number of bonds

of the atoms that participate in

resonance

so that would be three bonds here

and you would divide those three bonds

which

are basically part of those two atoms

so those three bonds are connected to

those two atoms not including the

central atom

so you can think of it as the three

bonds being shared across two atoms

so you get a bond order of 1.5

and it makes sense

here it looks like it's two here it's

one the resonance hybrid is actually an

average of the two

so it's 1.5

so that's the bottom order

for the two carbon oxygen bonds

now what about the solve for oxygen

bonds what's the bond order there

first let's calculate it and then let's

make sense of it this negative charge

can be shared among these three oxygen

atoms so all of those three oxygen atoms

they can have a single Bond or a double

bond

so to calculate the bond order

we have five Bonds in this system of

resonance

and those five bonds are spread out

across three oxygen atoms

so 5 divided by 3 that's 1.67

now let's draw the resonance structures

for this group

so this is one form

we can also put the oxygen there I mean

the negative charge on that oxygen

and we can also put the negative charge

on the oxygen in the bottom

so let's focus on this Bond

here it appears to have a bond order of

two

here it looks like it's one and here it

looks like it's two

if we were to average two one and two

what would what number will we get

so two plus one plus two

that's three numbers so we're going to

divide it by the three numbers

so we get five over three

so the bond order

for the sulfur oxygen

is 1.67 or 5 over 3.

so what it really means is that

out of the three resonance forms

two of them is going to have a double

bond one is going to have a single Bond

so you get an average of 1.67

so that's another way to picture a bond

order and now you know how to calculate

it when dealing with Organic resonance

structures