Problem 65 - General Chemistry: Principles and Modern Applications

Question

Each of the following molecules contains one or more multiple covalent bonds. Draw plausible Lewis structures to represent this fact, and predict the shape of each molecule. (a) \(\mathrm{CO}_{2} ;\) (b) \(\mathrm{Cl}_{2} \mathrm{CO} ;\) (c) CINO \(_{2}\).

Step-by-Step Solution

Answer

The \(\mathrm{CO}_2\) molecule has a linear shape, the \(\mathrm{Cl}_2 \mathrm{CO}\) molecule has a trigonal planar shape and the CINO \(_{2}\) molecule has a linear shape.

Step 1: Draw the Lewis Structure for \(\mathrm{CO}_2\)

The carbon atom has 4 valence electrons, and each oxygen atom has 6. Form a double bond between Carbon (C) and each Oxygen (O), which accounts for 8 electrons. Complete the octet for each Oxygen by adding lone pairs, which accounts for remaining electrons. The molecule is linear.

Step 2: Draw the Lewis Structure for \(\mathrm{Cl}_2 \mathrm{CO}\)

Carbon (C) is the central atom, bonded to an Oxygen atom and two Chlorine atoms. Carbon has 4 valence electrons, Oxygen has 6, and each Chlorine atom possesses 7. Form a double bond between Carbon and Oxygen, and single bonds between Carbon and each Chlorine atom, which accounts for 8 electrons. Complete the octets for Oxygen and the two Chlorine atoms by adding lone pairs. The shape is trigonal planar.

Step 3: Draw the Lewis Structure for CINO \(_{2}\)

Carbon (C) is the central atom, bonded to a Nitrogen atom and two Oxygen atoms. Carbon has 4 valence electrons, Nitrogen has 5 and each Oxygen atom possesses 6. Form a double bond between Carbon and each Oxygen atom, and a triple bond between Carbon and Nitrogen. The shape is linear.

Key Concepts

Covalent Bonds

Covalent bonds are a type of chemical bond where atoms share pairs of electrons. These bonds are fundamental in forming molecules and determining their structures.
In the exercise provided, molecules such as

• Carbon dioxide ( \( \mathrm{CO}_2 \) ),
• Dichloromethanone ( \( \mathrm{Cl}_2 \mathrm{CO} \) ),
• Chlorine Oxide Nitrate ( \( \mathrm{CINO}_2 \) )

all contain multiple covalent bonds.
This sharing of electrons ensures that each atom achieves a stable electronic configuration resembling that of a noble gas.
For example, in \( \mathrm{CO}_2 \), each oxygen atom forms a double covalent bond with the carbon atom, involving the sharing of two electron pairs. Similarly, in\( \mathrm{Cl}_2 \mathrm{CO} \), carbon shares electrons with oxygen via a double bond while forming single bonds with chlorine, achieving its octet. Lastly, in\( \mathrm{CINO}_2 \), carbon creates both double bonds with oxygen atoms and a triple bond with a nitrogen atom to achieve stability.

Molecular Geometry

Molecular geometry is concerned with the three-dimensional arrangement of atoms within a molecule, which affects the molecule’s properties and reactivity.
Understanding the geometry can give insights into the molecule's behavior.

• Linear shapes are found when there are two regions of electron density around a central atom. An example is \( \mathrm{CO}_2 \) , where the bond angle is 180°.
• Trigonal planar shapes are observed when there are three regions of electron density, with approximately 120° bond angles, as displayed in \( \mathrm{Cl}_2 \mathrm{CO} \) .

The shape of a molecule significantly influences its properties like polarity, reactivity, and even color. By drawing Lewis structures and applying the VSEPR (Valence Shell Electron Pair Repulsion) theory, it becomes easier to predict these shapes. In the case of \( \mathrm{CINO}_2 \), the linear arrangement of atoms signifies that all atoms in this molecule fall along a straight line.

Valence Electrons

Valence electrons are the outermost electrons of an atom and are crucial when it comes to bonding and chemical reactions.
They are the electrons involved in forming covalent bonds.

• In carbon, there are four valence electrons which play a pivotal role in its ability to form four bonds, as seen in all the molecules addressed in the exercise.
• Oxygen, having six valence electrons, generally seeks to complete its octet by forming two additional bonds, like in \( \mathrm{CO}_2 \)
• Nitrogen, with five valence electrons, is inclined to form three bonds to complete its octet, contributing to the triple bond seen in \( \mathrm{CINO}_2 \)

Understanding valence electrons is fundamental in predicting how atoms will interact and bond with each other, affecting the chemical properties and reactivity of the compounds.