Ethene (C2H4) Lewis Structure, Hybridization
Ethene's lewis structure can be built by VSEPR rule. Most stable structure is taken as the lewis structure of ethene. Hybridization of atoms in ethene molecue can be found from lewis structure. Each step of determining the lewis structure of ethene and hybridization are explained in this tutorial.
Ethene| C2H4
Ethene is the simplest alkene compound in alkene compound series. There are two carbon atoms and six hydrogen atoms in ethene molecule.
Lewis structure of ethene
Most stable and lewis structure of ethene is shown below. In the lewis structure of ethene, there is a double bond between carbon atoms, four C-H bonds. There are no lone pairs on atoms in the lewis structure of ethene.
 lewis structure.jpg "ethene (ethylene - C2H4) lewis structure")
Hybridization of ethene
Carbon atoms have sp2 hybridization. Hydrogen atoms are not hybridized because it has only s orbital. Therefore, hydrogen only contribute with s orbital to form bonds.
Simple method to determine the hybridization of atoms
VSEPR theory - Steps of drawing lewis structure of ethene
Following steps are followed to draw the ethene's lewis structure. Those steps are explained in detail in next sections. If you are a beginner to lewis structure drawing, follow these sections slowly and properly to understand it completely. Look the figures to understand each step.
- Find total number of electrons of the valance shells of carbon and hydrogen atoms
- Total electrons pairs
- Center atom selection
- Put lone pairs on atoms
- Check the stability and minimize charges on atoms by converting lone pairs to bonds until most stable structure is obtained.
Total number of electrons of the valance shells of ethene
Carbon belongs to the group IVA elements series. Therefore, it has four electrons in its valence shell. Hydrogen has only one electron in its valence shell. To find number of valence electron , these valence electrons of each element should be multiplied with their respective number of atoms in the molecule. Below, That step are done.
- Total valence electrons given by two carbon atoms = 4 * 2 = 8
There are four hydrogen atoms in ethene molecule, Therefore
- Total valence electrons given by hydrogen atoms = 1 * 4 = 8
There are no charges in ethene molecule. Therefore, no addition or reduction of valence electrons due to charges.
- Total valence electrons = 8 + 4 = 12
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, ethene molecule, Total number of pairs of electrons are 6.
Center atom and sketch of ethene molecule
There are some requirements to be the center atom. Having a high valence is a main requirement to be a center atom. For ethene molecule, carbon has the highest valence than and hydrogen.
Hydrogen cannot be a center atom because its valence is limited to one and hydrogen can keep only two electrons in its valence shell. Therefore, following sketch (structure of atoms) can be proposed for ethene.
Mark lone pairs on atoms
After drawing the sketch, we should start to mark lone pairs on atoms. In the drawn sketch, there are five bonds. between atoms.
- There are already one C-C bond and four C-H bonds in the above sketch. Therefore, there are five bonds (valence electron pairs). Now, there are only one (6-5 = 1) valence electrons pairs are remaining to draw (as mark lone pairs) the rest of the structure.
- Mark remaining valence electrons pair as a lone pairs on one carbon atom.
- Now, all valence electron pairs are marked as bonds and lone pairs.
Charges on atoms
Charges on atoms are 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. One carbin atoms will get a -1 charge and other carbon atom get a +1 charge. Because ethene is a neutral molecule, overall charge of the molecule should be zero. The overall charge of the molecule is, (-)1*1 + (+1) = 0.
Check the stability and minimize charges on atoms by converting lone pairs to bonds
When there are charges on lot of atoms in an ion or molecule, that structure is not stable. Therefore, We should try to reduce charges on atoms if it is a possible. Now, we are going to reduce charges on drawn structure.
- Now, we should try to minimize charges by converting a lone pair or pairs to a bond. So convert the lone pair on carbon atom to make a new C-C bond with other carbon atom as the following figure.
- Now there is a double bond between carbon atoms. Now, there are four single C-H bonds between carbon atoms and other hydrogen atoms.
You can see, there are no charges in atoms. therefore, this structure should be stable than the previous structure. Therefore, this structure is the lewis structure of ethene.
Questions
Can I draw resonance structures of C2H4 from the lewis structure of C2H4?
To know whether resonance structures can be drawn for C2H4, you should understand the structure of lewis structure of C2H4. In the lewis structure of C2H4, there are only four C-H bonds, one C=C bond and no lone pairs on last shells. There are only single bond between carbon atom and hydrogen atom because hydrogen caannot keep more than two electrons in it's last shell. Therefore, there cannot be more than one stable resonance structure for C2H4.
What are the tips, we can use to determine lewis structure of ethene?
- Hydrogen cannot make two bonds around it. So, hydrogen atoms always should be connected to carbon atoms. Also, there should be a bond between carbon atoms.
- If you are good at lewis structure drawing and organic chemistry, you can directly draw the ethene lewis structure. Because, ethene is an alkene compound, there should be a double between two carbon atoms. So rest of hydrogen atoms should be connected to those arbon atoms.
