Acetylene Formula: Structure, Bond Angle, Dipole Moment, Lewis Structure

The Structure Of Acetylene

Formula of acetylene

The structure of acetylene can be classified as a hydrocarbon because it consists of carbon and hydrogen atoms. It has two carbons and contains an unsaturated hydrocarbon consisting of a triple bond between the atoms of carbon and two sigma bonds with the hydrogen) atoms.

Eth- is the name of the parent, with "-yne" added as a suffix for triple bonds. Hence, ethyne is the IUPAC name. C2H2 is the chemical formula of acetylene.

The molar mass of acetylene

Use this formula to calculate the molar mass of C2H2

Molecular mass = 2 x (atomic mass of C(carbon) atom) + 2 x (atomic mass of H (hydrogen atom))

= 2 X (12.010)+ 2 X (01.007) = 26.040 g per mol

Hence, 026.040 g is the weight of 1 mole of acetylene formula.

Acetylene hybridization

Each carbon atom has sp-hybridization in ethyne. In the ground state of carbon, there are two electrons in the 2s orbital and one electron each in the 2Px and 2Py orbitals. 2Pz orbitals are empty. However, in its excited state, the paired electron pops out of the 2s orbital and fills the empty 2Pz orbital. So there are four orbitals 2s, 2Px, 2Py and 2Pz which are individually paired and willingly accept electrons from other atoms. However, there is a difference in how they overlap. In sp-acetylenic hybridization, the single electrons present in the 2Py and 2Pz orbitals are not hybridised. Instead, they overlap laterally with the unhybridized 2Pz and 2Py atomic orbitals of another carbon atom.

This forms a C-C triple bond. It includes the following:

1. The sigma (σ) bond is formed by the carbon atoms overlapping sp orbitals.

2. Pi (π) bonds are formed when unhybridized 2py orbitals overlap laterally.

3. Pi (π) bonds are formed by the lateral overlap of unhybridized 2Pz orbitals.

This 2sp hybrid orbital of ethyne (C2H2) forms a linear structure with a bond angle of 180 degrees.

Molecular Geometry

All the atoms present in ethyne lie in the same plane. There is no asymmetry present in the molecule. Therefore, C2H2 has a linear molecular geometry.

Bond Angle

Acetylene is an example of an unsaturated hydrocarbon. This is due to the triple bond formed by its two carbon atoms. The carbon-carbon triple bond results in the placement of all four atoms in the same straight line. As a result, acetylene has a bond angle of 180o.

Dipole Moment

C2H2 is composed of two types of atoms: carbon and hydrogen. The electronegativity difference between carbon and hydrogen is approximately 0.35, less than 0.4. Therefore, the C-H bond is nonpolar. Moreover, the atoms of ethyne are arranged linearly, so the distribution is uniform on both sides. Therefore, even if there is a dipole moment, it will be cancelled because the direction is opposite. Therefore, ethyne is a non-polar molecule.

Acetylene Lewis Structure

An atom of carbon has four valence electrons in its outer shell. Ethyne has two carbon atoms. Therefore, the carbon atom of C2H2 has eight valence electrons. An atom of hydrogen has one valence electron that is present in its outer shell. Therefore, a hydrogen atom has two valence electrons.

C2H2 valence electrons = 8 + 2 = 10

The C2H2 molecule has 10 valence electrons.

In the Lewis structure, both carbon atoms are centred because the carbon atom has a higher valence than the hydrogen atom. So two carbon atoms occupy the central position, and hydrogen atoms are arranged around them. Both the hydrogen atoms will have to share one valence electron of the carbon atom to form a bond.

The couple of both hydrogen atoms is complete now, but the octet of carbon atoms is not yet complete. So, to attain a structure that is stable, the carbon atom will have to share the three valence electrons that are remaining with the help of a triple bond. A total of six valence electrons out of 10 valence electrons are used to form a triple bond. It is formed between carbon atoms. In the Lewis structure of C2H2, the octets of all the atoms are completely filled, and no lone pairs of electrons are left in the molecule.