Choose The Correct Lewis Structure For C2H2

When it comes to drawing Lewis structures, it can be confusing to determine the correct arrangement of atoms and electrons. In this article, we will explore how to choose the correct Lewis structure for C2H2 (acetylene) and understand the bonding in this molecule.

Understanding Lewis Structures

Before we delve into the Lewis structure of C2H2, let’s first understand what a Lewis structure is. A Lewis structure is a diagram that shows the bonding between atoms in a molecule and the arrangement of electrons around them. In these structures, valence electrons are represented as dots or lines between atoms.

When drawing Lewis structures, it is essential to follow the octet rule, which states that atoms tend to gain, lose, or share electrons to achieve a full outer shell of eight electrons, known as the octet.

The Correct Lewis Structure for C2H2

C2H2 is the chemical formula for acetylene, a simple hydrocarbon composed of two carbon atoms and two hydrogen atoms. To determine the correct Lewis structure for C2H2, we need to consider the valence electrons of each atom and their bonding behavior.

Step 1: Count the Total Valence Electrons

To start, we must calculate the total number of valence electrons present in the molecule. Carbon has four valence electrons, while hydrogen has one. Since there are two carbon atoms and two hydrogen atoms in C2H2, the total number of valence electrons is:

2 (C) x 4 + 2 (H) x 1 = 10 valence electrons

Step 2: Determine the Skeleton Structure

Next, we need to arrange the atoms in a way that makes sense for the molecule. In acetylene, two carbon atoms are triple-bonded to each other, with a hydrogen atom bonded to each carbon. The skeleton structure for C2H2 looks like this:


H - C ≡ C - H

Step 3: Distribute Electrons and Form Bonds

Now, we distribute the remaining valence electrons around the atoms to complete their octets. Each carbon atom should have a total of eight electrons, while each hydrogen atom should have two. The final Lewis structure for C2H2 looks like this:


H H
\ /
C≡C

Step 4: Checking Formal Charge

To ensure the stability of the molecule, we need to calculate the formal charge of each atom. The formula for formal charge is:

Formal Charge = Valence Electrons – (Non-bonding Electrons + 0.5 x Bonding Electrons)

After calculating the formal charge for each atom, we find that the Lewis structure above satisfies the octet rule and minimizes formal charges, making it the correct structure for C2H2.

Key Points to Remember

  • Acetylene (C2H2) is a linear molecule composed of two carbon atoms triple-bonded to each other, with a hydrogen atom bonded to each carbon.
  • The correct Lewis structure for C2H2 follows the octet rule, with each atom having a full outer shell of electrons.
  • It is essential to calculate formal charges and ensure stability when choosing the correct Lewis structure for a molecule.

Conclusion

Choosing the correct Lewis structure for a molecule like C2H2 involves understanding the bonding behavior of atoms and following the octet rule. By carefully calculating valence electrons, arranging atoms, and distributing electrons, we can determine the most stable arrangement of atoms and electrons in a molecule.

Remember to always check formal charges and ensure that the Lewis structure satisfies the octet rule to find the correct arrangement for a given molecule.

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