Question

Calculate the formal charge on each atom in structures A-E comment on the relative importance of each structure. 10 lo=slo 이 10-S-01 S-0] ols=0 10=8-0 IsI0 0 B1 B2 B4 %3D0l jo-35-01 10 -S-01 10-S-0 %3D 0 3 %3D01 10--0 10 = 01 10%3D

Answer 1

Formula for calculation of Formal Charge is,

Formal charge VE NE-BE 2 (

Where, VE = Number of Valence Electron

NE = Number of Non bonding Electrons

BE = Number of Bonding Electrons.

Now,lets loot a the given structures and. Find out the formal charges using the above formula,

All the structure given contains only O and S atoms.

For O-atoms, VE = 6

For S-atoms, VE = 6

The atoms in these structures differ only in their NE and BE

Structure-A:

In Structure-A all the four O-atoms are similar so they have the same formal charge(FC).

electrons. pair ot These ines rcepreesent the lone 1O -S - T These ines reprcesents the 01 bond pair electrcoos

One Lone Pair of electron contains 2 electrons and one Bond Pair electron contains 2 electrons.

Each Oxygen has 3 lone pairs which means 6 non bonding electrons (NE = 6}

Each oxygen has 1 bond pair which means 2 bonding electrons (BE = 2)

VE of oxygen = 6

FC of Oxygen = 6 - 6 - (2/2) = -1

Each Sulfur has 0 lone pairs so, NE = 0

Each sulfur has 4 bond pairs so, BE = 8

VE of Sulfur = 6

FC of Sulfur = 6 - 0 - (8/2) = +2

Formal charges:

-2 101 101

Structure-B1:

NE- 4 BE =4 so, FC 6-4-40 11 NEE6 so, FC- 6- 6-2 BE 2 NE O +1 2 So FC =6-0-10 BE 10 Formal changes -1 I01 01 l0-4M0

Structure-B2:

7 NE 4 BF = 4 so, FC 6-4-4 -S=OI- NECO SO, FC=6-o- I01 -+1 2 BEE 10 NE-6 So FC 6- 6-2 7 BE 2 2 foremal charges -2 -1 IO1 -1 +1 10 501 -1

Structure-B3:

1 - 2 -1 0

Structure-B4:

- -1 IOI -1 1 IO

Look at structures B1, B2, B3 and B4 all are similar structures with different positioning of bonds. So, the atoms have similar formal charges.

Structure-C1:

NE=4 BE = 4 so FC 6- 4- -0 NE O (2 Se FC 6-0- 2 BE 12 1O1 NE E6 So FC = 6- 6- . 1 BE 2 Formal charge -2 IO 1 1

Structure-C2:

-1 1 10

Structure-C3:

_ -1 -1 101 0

Structures C1, C2 and C3 are similar different positioning of bonds so, the atoms has similar formal charges.

Structure-D:

NEE 4 FC = 6-4- 65 O BE =4 NE6 6-6-2 So fC= BE 2 1 NE O So FC=6-0-14 B6 14 -1 Foremal charges -2 11 1 10 O1o O1

Structure-E:

NE 4 10 11 So, FC = 6-4 -o BE- 4 0 1 1C NECO S FC6- 0-16 2 BE 16 Formal charges 11-: 1M4MO ol