Question

Draw the Lewis structures for carbon dioxide and carbon monoxide.

Short answer

The Lewis structures for carbon dioxide (CO2) and carbon monoxide (CO) are: Carbon dioxide (CO2): O=C=O Carbon monoxide (CO): :C≡O:

Step-by-step solution

Count valence electrons

For both molecules, we need to count the total number of valence electrons. Carbon has 4 valence electrons, and oxygen has 6 valence electrons. For carbon dioxide (CO2), we have: - 1 carbon atom: 4 valence electrons - 2 oxygen atoms: 2 * 6 valence electrons = 12 valence electrons Total valence electrons for CO2: 4 + 12 = 16 valence electrons For carbon monoxide (CO), we have: - 1 carbon atom: 4 valence electrons - 1 oxygen atom: 6 valence electrons Total valence electrons for CO: 4 + 6 = 10 valence electrons

Place the central atom

Since carbon is less electronegative than oxygen, we will place carbon in the center for both molecules. Carbon dioxide (CO2) looks like this: O-C-O Carbon monoxide (CO) looks like this: C-O

Distribute electrons

Now, we will distribute the electrons to create bonds. A single bond requires 2 electrons, so we will first use the valence electrons to form single bonds between the atoms. For carbon dioxide: - Between C and each O: 2 * 2 = 4 electrons (forming single bonds) We will have 12 electrons left (16 - 4 = 12) For carbon monoxide: - Between C and O: 2 electrons (forming a single bond) We will have 8 electrons left (10 - 2 = 8)

Fill the octet and determine bond types

Now, we will fill the octet for each atom and determine the bond types (single, double, or triple). For carbon dioxide: - Fill the octet for each O atom by adding 6 more electrons: 2 * 6 = 12 electrons Since we have used all 16 valence electrons, no further modification is needed. For carbon monoxide: - Fill the octet for O atom by adding 6 more electrons: 6 electrons Since we have only used 2 bonds to fill the oxygen atom's octet, 2 more electrons are needed to fill the octet for the carbon atom. We will thus form a triple bond between C and O. The Lewis structures for carbon dioxide (CO2) and carbon monoxide (CO) are as follows: Carbon dioxide (CO2): O=C=O Carbon monoxide (CO): :C≡O:

Key concepts

Valence Electrons

Understanding valence electrons is key to drawing Lewis structures correctly. Valence electrons are the electrons located in the outermost shell of an atom. They are essential because they determine how an atom will bond with others.
For example, carbon has 4 valence electrons, meaning it can form up to 4 covalent bonds with other atoms. Oxygen, on the other hand, has 6 valence electrons.

• Carbon: 4 valence electrons
• Oxygen: 6 valence electrons

Adding the valence electrons of all atoms in a molecule helps determine how electrons will be shared or transferred when forming bonds. In the case of carbon dioxide (CO2), the total is 16 valence electrons, and for carbon monoxide (CO) it's 10. Understanding the correct amount of valence electrons ensures the molecule achieves the most stable structure.

Carbon Dioxide

The Lewis structure of carbon dioxide (CO2) helps us understand its bonding and molecular shape. CO2 consists of one carbon atom and two oxygen atoms. When drawing its Lewis structure, carbon is placed in the center due to its lesser electronegativity compared to oxygen.
Carbon needs to form bonds to fulfill its 4 valence electrons, while each oxygen wants to complement its 6 valence electrons to reach 8, achieving the octet rule.

• Central Atom: Carbon (C)
• Bonding: Double bonds between Carbon and each Oxygen
• Total Electrons Used: 16

The resulting structure is depicted as O=C=O, where each oxygen forms a double bond with carbon. This arrangement satisfies the octet for both carbon and oxygen atoms, providing stability to the molecule.

Carbon Monoxide

Carbon monoxide (CO) has a distinct Lewis structure due to its unique properties and bonding requirements. CO is made of one carbon and one oxygen atom. Unlike CO2, CO features a triple bond to satisfy the octet rule for both atoms.
Initially, a single bond is formed using 2 valence electrons. However, to fulfill the octet rule for carbon, additional electrons are needed beyond the single bond.

• Central Atom: Carbon (C)
• Bonding: Triple bond between Carbon and Oxygen
• Total Electrons Used: 10

The produced structure for carbon monoxide is depicted as :C≡O:. This shows how carbon and oxygen share more electrons to stabilize the molecule, ensuring a complete octet for both elements.

Octet Rule

The Octet rule is a foundational guideline for drawing Lewis structures and understanding molecular stability. It refers to the tendency of atoms to prefer having 8 electrons in their valence shell, akin to noble gases.
In carbon dioxide and carbon monoxide, the octet rule is pivotal. Here’s how it works:

• Each Carbon atom aims to complete its four valence electrons to reach eight.
• Each Oxygen atom, having six valence electrons, seeks two more to fulfill the rule.

This principle influences the bonding patterns. CO2 achieves it with double bonds, while CO requires a triple bond. The octet rule ensures atoms achieve the lowest possible potential energy, contributing to the overall stability of the compound.