Question

Draw the Lewis structures of C2H6, C2H4, and C2H2.
Draw the molecules by placing atoms on the grid and connecting them with bonds. Include all hydrogen atoms.

Answer 1

Concepts and reason

The concept used to solve this question is to write the Lewis structures and structural formulas of the given molecules. The Lewis structure of the given molecules can be written by distributing the total number of valence electrons around the atoms in the molecule. The structural formula of the molecules represents the structure of the molecule by showing the bonds between the atoms.

Fundamentals

Lewis structures: Molecule chemical behavior can be understood by its structure, which involves the distribution of electron around each atom and type of bonding (single, double, triple). Lewis structure represents the electron distribution around atoms in the molecule. It is also known as electron dot structures which have following features.

1) These structures take into account only valence electrons.

2) These clearly show bonding and nonbonding electrons.

3) All atoms should obey the duet rule and the octet rule.

Octet rule: It states the atoms of main group elements in the molecule forms bonds in such a way that it has eight electrons in its valence shell.

Structural formula: It represents the structure of the molecule in which all bonds shown by placing the atoms in the framework. It also gives information about the arrangement of the atoms in the molecule.

The given formula of the molecule is ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{6}}}$ .

The number of valence electrons present in carbon atom is 4.

The number of valence electrons present in hydrogen atom is 1.

Thus, the total number of valence electrons in the given molecule can be calculated as follows:

$\begin{array}{c}\\{\rm{2(C) + 6(H) = 2(4) + 6(1)}}\\\\{\rm{ = 8 + 6}}\\\\{\rm{ = 14 valence electrons}}\\\end{array}$

These 14 electrons have to be arranged in the Lewis structure.

Hydrogen can form only one bond and carbon can form four bonds.

Draw the Lewis structure for individual atoms C and Hs.

And, two electrons can form one covalent bond (single bond) between two atoms. The C-atom in the molecule should follow the octet rule.

Hence, the Lewis structure of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{6}}}$ can be drawn by using the above information as follows:

The given formula of the molecule is ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{4}}}$ .

The number of valence electrons present in carbon atom is 4.

The number of valence electrons present in hydrogen atom is 1.

Thus, the total number of valence electrons in the given molecule can be calculated as follows:

$\begin{array}{c}\\{\rm{2(C) + 4(H) = 2(4) + 4(1)}}\\\\{\rm{ = 8 + 4}}\\\\{\rm{ = 12 valence electrons}}\\\end{array}$

These 12 electrons have to be arranged in the Lewis structure.

Hydrogen can form only one bond and carbon can form four bonds.

Draw the Lewis structure for individual atoms C and Hs.

And, two electrons can form one covalent bond (single bond) and four electrons can form double bond between atoms. The C-atom in the molecule should follow the octet rule.

Hence, the Lewis structure of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{4}}}$ can be drawn by using the above information as follows:

The given formula of the molecule is ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_2}$ .

The number of valence electrons present in carbon atom is 4.

The number of valence electrons present in hydrogen atom is 1.

Thus, the total number of valence electrons in the given molecule can be calculated as follows:

$\begin{array}{c}\\{\rm{2(C) + 2(H) = 2(4) + 2(1)}}\\\\{\rm{ = 8 + 2}}\\\\{\rm{ = 10 valence electrons}}\\\end{array}$

These 10 electrons have to be arranged in the Lewis structure.

Hydrogen can form only one bond and carbon can form four bonds.

The Lewis structure for individual atoms C and Hs can be written as follows:

And, two electrons can form one covalent bond (single bond) and six electrons can form triple bond between atoms. The C-atom in this molecule should follow the octet rule.

Hence, the Lewis structure of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_2}$ can be drawn by using the above information as follows:

The Lewis structure of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{6}}}$ is shown below.

In the above Lewis structure, a pair of electrons shows a single bond.

Thus, a single bond is present between two C-atoms and each carbon atom has three single bonds with three hydrogen atoms.

Therefore, the structural formula of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{6}}}$ can be drawn as follows:

The Lewis structure of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{4}}}$ is shown below.

In the above Lewis structure, a pair of electrons shows a single bond.

Thus, a double bond is present between two C-atoms and each carbon atom has two single bonds with two hydrogen atoms.

Therefore, the structural formula of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{4}}}$ can be drawn as follows:

The Lewis structure of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{2}}}$ is shown below.

In the above Lewis structure, a pair of electrons shows a single bond.

Thus, a triple bond is present between two C-atoms and each carbon atom has one single bond with one hydrogen atom.

Therefore, the structural formula of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{2}}}$ can be drawn as follows:

$H-C=C—H $

Ans: Part 1.a

The Lewis structure of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{6}}}$ is shown below.

Part 1.b

The Lewis structure of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{4}}}$ is shown below.

Part 1.c

The Lewis structure of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_2}$ is shown below.

Part 2.a

The structural formula of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{6}}}$ indicating all bonds is shown below.

Part 2.b

The structural formula of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{4}}}$ indicating all bonds is shown below.

Part 2.c

The structural formula of ${{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{2}}}$ indicating all bonds is shown below.

$H-C=C—H $