How to calculate formal charges of sulfuric acid (H2SO4) with lewis structure?

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In covalently bonded molecules, formal charge is the charge assigned to an atom based on the assumption that the bonded electrons are equally shared between concerning atoms, regardless of their electronegativity.

The overall formal charge present on a molecule is a measure of its stability.

The fewer the formal charges present on the bonded atoms in a molecule (close to zero), the greater the stability of its Lewis structure.

In this article, we will calculate the formal charges present on the bonded atoms in the king of chemicals, i.e., sulfuric acid (H2SO4), and its overall charge.

So, continue reading!

Name of the molecule Sulfuric acid 
Chemical formulaH2SO4
The formal charge on the sulfur (S) atom0
The formal charge on each S=O bonded oxygen (O) atom0
The formal charge on each S-O-H bonded oxygen (O) atom0
The formal charge on each hydrogen (H) atom
0
The overall formal charge on H2SO4
0

How to calculate the formal charges on H2SO4 atoms?

The formal charges can be calculated using the formula given below:

formal charge formula

The formal charge of an atom = [valence electrons of an atom – non-bonding electrons – ½ (bonding electrons)]

  • The valence electrons (V.E) of an atom are the total number of electrons present in its valence shell. Valence electrons can be calculated by locating the position of the elemental atom in the Periodic Table.
  • Non-bonding electrons (N.E) are the number of lone pairs present on the atom. (1 lone pair means 2 nonbonding electrons).
  • Bonding electrons (B.E) are the total electrons shared with the atom via covalent chemical bonds. (1 single bond means 2 bonding electrons).

The most preferred Lewis representation of sulfuric acid (H2SO4) is as shown below.

most stable H2SO4 lewis structure

It consists of a total of 32 valence electrons. A Sulfur S-atom is present at the center. It is double-bonded to two oxygen (O) atoms and single-bonded to two hydroxyls (OH) functional groups.

No lone pair of electrons is present at the central S-atom or at any of the two H-atoms. Contrarily, each oxygen atom carries two lone pairs of electrons in the above Lewis structure.

It is the best possible Lewis structure of H2SO4 because the formal charges are minimized in it, and thus, it is also the most stable.

Now let’s find the formal charges present on each atom in the most stable H2SO4 Lewis structure by applying the formal charge formula given above.

For the sulfur atom

calculating formal charge on sulfur atom in H2SO4

  • Valence electrons of Sulfur = It is present in Group VI A = 6 valence electrons
  • Bonding electrons = 2 single bonds + 2 double bonds = 2(2) + 2(4) = 12 electrons
  • Non-bonding electrons = no lone pair = 0 electrons
  • Formal charge = 6 – 0 – 12/2 = 6 – 0 – 6 = 6 – 6 = 0

The formal charge on the central sulfur (S) atom in H2SO4 is 0.

For each S=O bonded oxygen atom

calculating formal charge on double bonded oxygen atom in H2SO4

  • Valence electrons of oxygen = It is present in Group VI A = 6 valence electrons
  • Bonding electrons = 1 double bond = 4 electrons
  • Non-bonding electrons = 2 lone pairs = 2(2) = 4 electrons
  • Formal charge = 6 – 4 – 4/2 = 6 – 4 – 2 = 6 – 6 = 0

The formal charge on each S=O double-bonded oxygen (O) atom in H2SO4 is 0.

For each S-O-H bonded oxygen atom

calculating formal charge on single bonded oxygen atom in H2SO4

  • Valence electrons of oxygen = It is present in Group VI A = 6 valence electrons
  • Bonding electrons = 2 single bonds = 2 + 2 = 4 electrons
  • Non-bonding electrons = 2 lone pairs = 2(2) = 4 electrons
  • Formal charge = 6 – 4 – 4/2 = 6 – 4 – 2 = 6 – 6 = 0

The formal charge on each S-O-H bonded oxygen (O) atom in H2SO4 is also 0.

For each hydrogen atom

calculating formal charge on hydrogen atom in H2SO4

  • Valence electrons of hydrogen = It is present in Group I A = 1 valence electron
  • Bonding electrons = 1 single bond = 2 electrons
  • Non-bonding electrons = no lone pairs = 0 electrons
  • Formal charge = 1 – 0 – 2/2 = 1 – 0 – 1 = 1– 1 = 0

The formal charge on each hydrogen (H) atom in H2SO4 is 0.

As per the above calculation, zero or no formal charges are present on the bonded atoms in the H2SO4 Lewis structure.

H2SO4 lewis structure with formal charge

Therefore, there is no overall charge present on H2SO4. This denotes that sulfuric acid is a neutral molecule.

H2SO4 formal charge

 

Also, check –

FAQ

How can you calculate H2SO4 formal charges?

The formal charges present on the bonded atoms in H2SO4 can be calculated using the formula given below:

V.E – N.E – B.E/2

Where –

⇒ V.E = valence electrons of an atom

⇒ N.E = non-bonding electrons, i.e., lone pairs

⇒ B.E = bonding electrons

What is the formal charge on S-atom in H2SO4?

The central sulfur (S) atom carries zero or no formal charges in H2SO4.

What are the formal charges on each oxygen atom in H2SO4?

Zero or no formal charges are present on each of the four oxygen atoms in the H2SO4 Lewis structure.

What are the formal charges on each hydrogen atom in H2SO4?

Both the H-atoms carry zero or no formal charges in the H2SO4 Lewis structure.

Do all the bonded atoms carry the same formal charges in the H2SO4 Lewis structure?

Yes. All the bonded atoms, i.e., a sulfur atom, two hydrogen atoms, and four oxygen atoms, carry the same, i.e., zero or no formal charges in the H2SO4 Lewis structure.

What is the overall charge present on H2SO4?

No overall formal charges are present on the H2SO4 Lewis structure. Thus, it is a neutral molecule.

Summary

  • The best possible Lewis structure of a molecule is the one in which the bonded atoms carry formal charges as close to zero as possible.
  • The formal charge formula is [ V.E – N.E – B.E/2].
  • In H2SO4, a zero formal charge is present on the central S-atom.
  • Each of the four O-atoms and two H-atoms carries zero formal charges in H2SO4.
  • No overall formal charge is present on the H2SO4 which denotes that it is a neutral molecule.
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