Structure, Molecular Geometry, and Hybridization of CH2O

Formaldehyde has the formula CH2O and is the most common and simplest aldehyde ever discovered. By removing one hydrogen atom from alcohol, formaldehyde can be generated.

Formaldehyde has long been an essential preservative due to its ability to eliminate harmful infections and inhibit the growth of germs.

Formaldehyde is also well-known for being extremely unpleasant to the sense of smell, deteriorating for humans, and a recognised carcinogen.

Lewis structure diagrams reveal precisely how many valence electrons are available within an atom and contribute to bond formation.

The Lewis structure facilitates the visualisation of the behaviour of the valence electrons within the molecule and the presence or absence of lone pairs of electrons.

The structure consists of electrons depicted as dots, often in pairs, surrounding the atom symbol.

Additionally, the bond creation is represented by lines whose numbers indicate whether a single, double, or triple bond is created within the molecule.

What are the electrons of Valence?

The outer shell of an atom contains the valence electrons, which actively participate in bond formation by being donated or accepted.

As they are present in the outermost shell, the nucleus’ hold on the outermost shell’s valence electrons is weak.

To stabilise their octet, the valence electrons can readily engage in bond formation. According to the octet rule, the maximum number of electrons an atom can have is eight.

What is the rule of eight?

The maximum number of valence electrons an atom may hold in its outermost shell is eight, according to the rule.

It stems from the necessity of achieving an electrical configuration comparable to that of noble gases. Therefore, all computations will be performed assuming that the maximum number of atoms is eight.

In addition, in the lewis structure, electrons are always drawn in pairs, whereas unpaired electrons typically indicate a lack of valence electrons.

Carbon has an atomic number of six and an electrical configuration of 1s2 2s2 2p2. As the p shell can accommodate up to six electrons, only four electrons remain.

Therefore, four electrons are required to complete carbon’s octet.

Hydrogen possesses an atomic number of one and an electrical configuration of 1s1.

As the s shell can hold up to two electrons, but there is a scarcity of only one, a hydrogen atom requires only one valence electron to complete its shell.

Now, the atomic number of the oxygen atom is eight, and its electronic configuration is 1s2 2s2 2p4. As the p shell can accommodate six electrons, only two are in short supply.

This results in a maximum of six valence electrons per oxygen atom.

The more valence electrons an atom has, the easier it is for it to acquire electrons, while the fewer valence electrons it has, the easier it is for it to donate electrons to stabilise its octet.

This indicates that oxygen and hydrogen have a higher electronegativity, or the tendency to attract shared electrons in pairs, than carbon.

Therefore, the carbon with the least electronegative charge in the CH2O molecule is preserved at the centre of the lewis diagram you will examine in the subsequent subtopic.

CH2O Lewis Structure

Formaldehyde is a tetraatomic molecule in which hydrogen, carbon, and oxygen atoms utilise a variable number of valence electrons to neutralise the formal charge.

The Lewis Structure of H2O is depicted as follows:

  1. Determine the total number of valence electrons already available in a single formaldehyde CH2O molecule: Two come from the two hydrogen atoms, four from the carbon atom, and six from the oxygen atom, for a total of twelve.
  2. Determine how many additional electrons are required to stabilise the octet of all the interacting atoms: for a single CH2O molecule, the required number is eight, as the oxygen atom requires two, the carbon atom requires four, and the two hydrogen atoms require one electron each.

Determine the sort of bonding occurring within the CH2O molecule: A double bond is developing between the carbon and oxygen atoms, whereas each carbon and hydrogen atom is making a single bond.

Look for the core atom, which in the case of CH2O is carbon because carbon has the lowest electronegativity.

In addition, if carbon is the core atom of the CH2O molecule, it is simpler to neutralise the formal charge distribution throughout the molecule.

  1. Depict the Lewis Structure as a skeleton

How can formal charge distribution on each atom be calculated?

It can be accomplished using the formula:

Valence Electrons – Unbonded Electrons – 12 Bonded Electrons = Formal Charge

Zero is the value for each atom.

Why does CH2O contain a double bond between its carbon and oxygen atoms?

The carbon atom must have eight valence electrons comparable to those of oxygen. In contrast, a single hydrogen atom requires only two valence electrons.

The diagram below illustrates the existence of a single bond between oxygen and carbon atoms.

This arrangement is only stabilising the hydrogen and oxygen atoms since the carbon atom is missing two electrons.

The octet of carbon can only be filled through the formation of a double bond between carbon and oxygen. Hydrogen atoms are incapable of participating in this bonding in any way.

In addition, if you think about it, the formal charge in a Lewis structure with a double bond is fully neutralised.

CH2O Molecular Geometry

The bond angles for the hydrogen-carbon-hydrogen (H-C-H) and the hydrogen-carbon-oxygen (H-C-O) atoms are 116° and 122°, respectively, and the structure is bent.

In addition, the Valence Shell Electron Pair Repulsion (VSEPR) theory states that a molecule’s molecular geometry is trigonal planar if the bond angle is 120 degrees or less.

This difference in bond angles from 120° is due to the presence of lone electron pairs on the oxygen atom, which distorts the CH2O molecule’s overall structure.

As is well known, lone pairs are attracted to the nucleus, whereas double bonds result in greater repulsion than single bonds; therefore, the bond angles deviate significantly from the ideal value of 120°.

Polarization of CH2O

The polarity of the formaldehyde (CH2O) molecule is due to the net dipole moment across the molecule.

The fact that oxygen is more electronegative than carbon causes it to draw bound pairs closer to itself and generate polarisation of charges.

You can also read an article on the polarity of CH2O to learn the cause for polarity in depth.

The CH2O hybridization molecule

Carbon’s hybridization in the CH2O molecule is sp2.

It can be calculated with the assistance of the following formula:

Total hybrid orbitals = sigma bond count plus lone pair count on the core atom.

In the case of a single bond, only one sigma bond exists. In the case of a double covalent bond, however, both sigma () and pi () bonds are present.

Therefore, the carbon atom in a single CH2O molecule forms three sigma bonds and no lone pairs.

Please notice that the two lone pairs are located on the oxygen atom and not the carbon atom, so they will not be taken into account.

So, according to the preceding calculation, the total number of hybrid orbitals is 3 + 0 = 3.

Only in the instance of sp2 hybridization are three new hybrid orbitals produced when one s orbital and two pi orbitals within the same shell of an atom overlap and mix.

Therefore, formaldehyde (CH2O) possesses sp2 hybridization.

In addition, these three new hybrid orbitals have similar energies, with 33.33 percent s orbital features and 66.66 percent p orbital characteristics.


The Lewis Structure of formaldehyde (CH2O) illustrates how the carbon, oxygen, and hydrogen atoms share electrons to neutralise the overall formal charge.

In addition, CH2O has a trigonal planar structure with bond angles that are somewhat deviated from the optimum value of 120°.

Due to the presence of a double bond and two pairs of unpaired electrons. In addition, the carbon hybridization in the CH2O molecule is sp2.

It may be researched in further depth with the aid of its molecular orbital diagram.

Read more: Polarity, CF4 Lewis Structure, Molecular Geometry, and Hybridization

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


Please enter your comment!
Please enter your name here

Read More