Lewis Structure of Sulfuric Acid (H2SO4) - Steps of Drawing

Lewis structure of sulfuric acid is drawn step by step in this tutorial. Total valence electrons concept is used to draw the lewis structure of H2SO4. Sulfuric acid is a strong dibasic acid.


Sulfuric acid | H2SO4

Sulfuric acid is a dibasic strong acid. It means, it can release two hydrogen atoms to show acidic characteristics. Therefore, we can assume, there should be two -OH bonds in sulfuric acid molecule.


Lewis structure of H2SO4

Most stable lewis structure of H2SO4 is shown below.

H2SO4 lewis structure


Steps of drawing lewis structure of H2SO4

Following steps are followed to draw theH2SO4 lewis structure and they are explained in detail in next sections. If you are are beginner to lewis structure drawing, follow these sections slowly and properly to understand.

  1. Find total number of electrons of the valance shells of sulfur, oxygen and hydrogen atoms
  2. Total electrons pairs
  3. Center atom selection
  4. Put lone pairs on atoms
  5. Check the stability and minimize charges on atoms by converting lone pairs to bonds until most stable structure is obtained.

Drawing the correct lewis structure is important to draw resonance structures correctly



Total number of electrons of the valance shells of H2SO4

Both Sulfur and oxygen atoms are located at VIA group in the periodic table. So, oxygen and sulfur atoms have six electrons in their valence shells. Hydrogen is IA group element. Therefore it has only one electron in its last shell. Now, we can find the total valence electrons in the molecule.


  • Total valence electrons given by sulfur atom = 6

There are four oxygen atoms in H2SO4 molecule, Therefore

  • Total valence electrons given by oxygen atoms = 6 *4 = 24

There are two hydrogen atoms in H2SO4 molecule, Therefore

  • Total valence electrons given by hydrogen atoms = 1*2 = 2

There are no charges in H2SO4 molecule.


  • Total valence electrons = 6 + 24 + 2 = 32


Total valence electrons pairs

Total valance electrons pairs = σ bonds + π bonds + lone pairs at valence shells

Total electron pairs are determined by dividing the number total valence electrons by two. For, H2SO4 molecule, Total pairs of electrons are 16.




Center atom and sketch of H2SO4 molecule

There are some requirements to be the center atom. Having a high valence is a leading requirement to be a center atom. For H2SO4 molecule, sulfur has the highest valence than oxygen and hydrogen.

Because, sulfuric acid is a dibasic acid, it can release two H+ ions in the water. Therefore, there should be two -OH groups in H2SO4 molecule.

H2SO4 skech structure.jpg

Mark lone pairs on atoms

  • There are already four S-O bonds and two O-H bonds in the above sketch. Therefore only twelve (16-6 = 10) valence electrons pairs are remaining to draw the rest of the structure.
  • Start to mark remaining ten valence electrons pairs as lone pairs on outside atoms (on oxygen atoms). All remaining valence electrons pairs can be marked on oxygen atoms. (oxygen atom cannot keep more than eight electrons in its valence shell).
  • Therefore, there is no electron pairs to mark on sulfur atom.
mark lone pairs on atoms in sulfuric acid lewis structure

Charges on atoms

Charges on atoms is important to find the most stable lewis structure. Therefore, we should try to find charges if there are.

After, marking electron pairs on atoms, we should mark charges of each atom. Two oxygen atoms will get a -1 charge and sulfur atom get a +2 charge. Sulfuric acid is a neutral molecule and overall charge should be zero. The overall charge of ion is ( -1*2 + (+2) ) = 0.

mark charges on atoms in H2SO4 lewis structure


Check the stability and minimize charges on atoms by converting lone pairs to bonds

When charges exist on lot of atoms in an ion or molecule, that structure is not stable. We should try to reduce charges on atoms as much as possible. Now, we are going to reduce charges on drawn structure.

  • Oxygen atoms should hold negative charges because electronegativity of oxygen is higher than sulfur. Otherwise, we can say, ability of holding negative charges is great in oxygen atoms than sulfur atoms.
  • The drawn structure has two -1 charges on two oxygen atoms.
  • Now, we should try to minimize charges by converting lone pair or pairs to bonds. So convert one lone pair of one oxygen atom to make a new S-O bond.
  • Now there is a double bond between sulfur atom and one oxygen atom. Now, there are three S-O single bonds between sulfur atom and other three oxygen atoms.
reduce charges on the sketch of H2SO4

You see charges of atoms are reduced. Now, there is no charge in one oxygen atom and charge of sulfur atom is reduced from +2 to +1. So we have an stable ion than out previous one.


Can I reduce charges of atoms furthermore?

You should know, sulfur can keep more than eight electrons in its last shell. Therefore we can convert one more lone pair of another oxygen atom to make a bond.

reduce charges furthermore on the sketch of H2SO4

In new structure, charges of atoms are reduced than previous structure. Now there are no charges on atoms. This structure of H2SO4 is more stable than previous structures. So, this structure has more chance to be the lewis structure of H2SO4.




Questions


how many single bonds are in the lewis structure for H2SO4?

There are two single bonds (S-O) around sulfur atom. Also, there are another two single bonds (O-H) between oxygen and hydrogen atom. Therefore, there are total of four single bonds in H2SO4.





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