Problem 61 - Chemistry: The Central Science

Question

Draw the dominant Lewis structures for these chlorine-oxygen molecules/ions: \(\mathrm{ClO}, \mathrm{ClO}^{-}, \mathrm{ClO}_{2}^{-}, \mathrm{ClO}_{3}^{-}, \mathrm{ClO}_{4}^{-} .\)Which of these do not obey the octet rule?

Step-by-Step Solution

Answer

The dominant Lewis structures for the given chlorine-oxygen molecules/ions are as follows: 1. ClO: Cl is single bonded to O, but Cl doesn't satisfy the octet rule with only 7 valence electrons. 2. ClO⁻, ClO₂⁻, ClO₃⁻, and ClO₄⁻: In each of these ions, Cl is single bonded to one or more O atoms, and all atoms satisfy the octet rule due to the additional electrons provided by the negative charge. Therefore, only ClO does not obey the octet rule.

Step 1: Determine the total number of valence electrons for each molecule/ion

First, let's find the total number of valence electrons in each molecule/ion. Chlorine (Cl) has 7 valence electrons, and Oxygen (O) has 6 valence electrons. For the ions, we also need to consider the charge. 1. ClO: 7 (from Cl) + 6 (from O) = 13 valence electrons 2. ClO⁻: 7 (from Cl) + 6 (from O) + 1 (from the negative charge) = 14 valence electrons 3. ClO₂⁻: 7 (from Cl) + 2 * 6 (from two O atoms) + 1 (from the negative charge) = 20 valence electrons 4. ClO₃⁻: 7 (from Cl) + 3 * 6 (from three O atoms) + 1 (from the negative charge) = 26 valence electrons 5. ClO₄⁻: 7 (from Cl) + 4 * 6 (from four O atoms) + 1 (from the negative charge) = 32 valence electrons

Step 2: Draw the dominant Lewis structures for each molecule/ion

Now, we can draw the Lewis structures for each molecule/ion. 1. ClO: - Connect Cl and O with a single bond - Distribute the remaining electrons to satisfy the octet rule for each atom if possible 2. ClO⁻: - Connect Cl and O with a single bond - Distribute the remaining electrons to satisfy the octet rule for each atom 3. ClO₂⁻: - Connect Cl to the two O atoms with single bonds - Distribute the remaining electrons to satisfy the octet rule for each atom 4. ClO₃⁻: - Connect Cl to the three O atoms with single bonds - Distribute the remaining electrons to satisfy the octet rule for each atom 5. ClO₄⁻: - Connect Cl to the four O atoms with single bonds - Distribute the remaining electrons to satisfy the octet rule for each atom

Step 3: Determine which structures do not obey the octet rule

Analyze each of the Lewis structures to determine if any do not obey the octet rule. 1. ClO: - Cl: 7 valence electrons (not satisfying the octet rule) - O: 8 valence electrons (satisfying the octet rule) 2. ClO⁻, ClO₂⁻, ClO₃⁻, and ClO₄⁻ all have atoms that satisfy the octet rule as the negative charge allows for the distribution of additional electrons. According to the analysis, only the ClO molecule does not obey the octet rule due to the chlorine atom having only 7 valence electrons.

Key Concepts

Valence Electrons

Understanding valence electrons is fundamental for predicting the chemical behavior of an atom in a molecule. Valence electrons are the outermost electrons of an atom and participate in chemical bonding. They are significant because they are the ones that atoms use to gain, lose, or share when forming chemical bonds.

For instance, chlorine (Cl) has 7 valence electrons, while oxygen (O) has 6. This total number of valence electrons available helps determine how atoms bond in a molecule or ion. When drawing Lewis structures, it's crucial to count these valence electrons accurately, as they provide the basis for understanding the molecular structure and charge distribution.

To illustrate, in the ClO molecule, there are 13 valence electrons to consider, whereas the ClO⁻ ion has an additional electron due to its negative charge, giving it 14 valence electrons to distribute when drawing its Lewis structure. Counting valence electrons accurately is the first step in creating reliable and representative Lewis structures.

Octet Rule

The octet rule is a simple guideline in chemistry stating that atoms are most stable when they have eight electrons in their valence shell, mimicking the electron configuration of a noble gas. This rule guides the arrangement of electrons in the Lewis structures and helps to predict the types of bonds that atoms will form to achieve a complete octet.

However, there are exceptions to the octet rule. Some species might have less than eight electrons (like in the case of the ClO molecule, where Cl has only 7 valence electrons) or even more than eight electrons. This occurs particularly with elements situated below the second row of the periodic table, which can exceed the octet by utilizing their empty d-orbitals.

Molecules or ions that do not satisfy the octet rule are sometimes less stable or reactive. Identifying if a Lewis structure obeys the octet rule helps in predicting the molecule's reactivity and the possibility of it participating in chemical reactions.

Chlorine-Oxygen Molecules/Ions

Chlorine-oxygen molecules and ions (such as ClO, ClO⁻, ClO₂⁻, ClO₃⁻, and ClO₄⁻) are important species in chemistry, each having distinctive structures and properties. The dominant Lewis structures for these chloroxy compounds help depict their bonding and electron distribution.

The process involves pairing chlorine and oxygen atoms through single bonds and distributing the remaining valence electrons to fill the octets. The presence of a negative charge on the ions increases the total number of valence electrons, allowing for a more flexible electron distribution. Not all of these species strictly follow the octet rule, as seen in the ClO molecule.

Analyzing these molecules helps in understanding concepts regarding stability, resonance, and the behavior of atoms that do not conform to the octet rule. It is noteworthy that chloroxy compounds play significant roles in various chemical reactions, including oxidation processes and in the stratospheric ozone layer's chemistry.