Question

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

Short answer

The dominant Lewis structures for the chlorine-oxygen molecules/ions are: 1. ClO: [(O with 3 non-bonding electron pairs) - (single bond) - (Cl with 2 non-bonding electron pairs and one electron without a pair)] 2. ClO⁻: [(O with 3 non-bonding electron pairs) - (single bond) - (Cl with 3 non-bonding electron pairs)] with a negative charge on Cl 3. ClO₂⁻: [(O with 3 non-bonding electron pairs) - (single bond) - (Cl with 2 non-bonding electron pairs) - (single bond) - (O with 3 non-bonding electron pairs)] with a negative charge on Cl 4. ClO₃⁻: [(O with 3 non-bonding electron pairs) - (single bond) - (Cl with 1 non-bonding electron pair) - (single bond) - (O with 3 non-bonding electron pairs)] and a third O single bonded to Cl as well, with a negative charge on Cl 5. ClO₄⁻: [(O with 3 non-bonding electron pairs) - (single bond) - (Cl without non-bonding electron pairs) - (single bond) - (O with 3 non-bonding electron pairs)] with two other oxygens single bonded to Cl, and a negative charge on Cl Out of these, only the ClO molecule does not obey the octet rule, as its Cl atom has only 7 valence electrons.

Step-by-step solution

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

First, let us find the number of valence electrons in each molecule or ion. Chlorine (Cl) has 7 valence electrons, while oxygen (O) has 6. And as we have negative charges on the ions, we'll need to add one electron for each negative charge. 1. ClO: 7 (from Cl) + 6 (from O) = 13 valence electrons 2. ClO⁻: 7 (from Cl) + 6 (from O) + 1 (for the negative charge) = 14 valence electrons 3. ClO₂⁻: 7 (from Cl) + 2×6 (from two O's) + 1 (for the negative charge) = 20 valence electrons 4. ClO₃⁻: 7 (from Cl) + 3×6 (from three O's) + 1 (for the negative charge) = 26 valence electrons 5. ClO₄⁻: 7 (from Cl) + 4×6 (from four O's) + 1 (for the negative charge) = 32 valence electrons

Draw the Lewis structures for each molecule/ion

Now, let's draw the dominant Lewis structures for each molecule/ion: 1. ClO: [(O with 3 non-bonding electron pairs) - (single bond) - (Cl with 2 non-bonding electron pairs and one electron without a pair)] 2. ClO⁻: [(O with 3 non-bonding electron pairs) - (single bond) - (Cl with 3 non-bonding electron pairs)] with a negative charge on Cl 3. ClO₂⁻: [(O with 3 non-bonding electron pairs) - (single bond) - (Cl with 2 non-bonding electron pairs) - (single bond) - (O with 3 non-bonding electron pairs)] with a negative charge on Cl 4. ClO₃⁻: [(O with 3 non-bonding electron pairs) - (single bond) - (Cl with 1 non-bonding electron pair) - (single bond) - (O with 3 non-bonding electron pairs)] and a third O (with 3 non-bonding electron pairs) single bonded to Cl as well, with a negative charge on Cl 5. ClO₄⁻: [(O with 3 non-bonding electron pairs) - (single bond) - (Cl without non-bonding electron pairs) - (single bond) - (O with 3 non-bonding electron pairs)] with the remaining two oxygens also single bonded to Cl, each with 3 non-bonding electron pairs, and a negative charge on Cl

Identify which structures do not obey the octet rule

Now we'll identify which of these structures do not obey the octet rule: 1. ClO: The Cl atom has only 7 valence electrons, so it does not obey the octet rule. 2. ClO⁻: All atoms have 8 valence electrons, so it obeys the octet rule. 3. ClO₂⁻: All atoms have 8 valence electrons, so it obeys the octet rule. 4. ClO₃⁻: All atoms have 8 valence electrons, so it obeys the octet rule. 5. ClO₄⁻: All atoms have 8 valence electrons, so it obeys the octet rule. So, only the ClO molecule does not obey the octet rule.

Key concepts

Chlorine-Oxygen Compounds

Chlorine-oxygen compounds are an interesting class of chemical species that consist of different combinations of chlorine (Cl) and oxygen (O) atoms. These compounds can exist both as neutral molecules and as ions with negative charges. Some common examples include

• Hypochlorite (ClO⁻)
• Chlorite (ClO₂⁻)
• Chlorate (ClO₃⁻)
• Perchlorate (ClO₄⁻)

These compounds have different oxidation states and reactivities, which affect how they interact chemically.

The addition of oxygen atoms affects the structure and properties of these compounds. Chlorine dioxide (ClO₂), for example, is used in water treatment, while hypochlorous acid (HClO) is used in disinfection. The varying number of oxygen atoms also influences stability and the ability to form ions, with more oxygen atoms typically resulting in a stronger oxidizing agent.

Their Lewis structures are crucial to understanding their reactivity and bonding characteristics. Drawing these structures helps visualize the arrangement of atoms and electrons, giving insight into which bonds may break or form in chemical reactions.

Octet Rule

The octet rule is a guiding principle in chemistry that states atoms strive to have eight electrons in their valence shell, resembling the electron configuration of noble gases. This rule is helpful in predicting how atoms will bond in molecules. For many atoms, particularly those in the second period of the periodic table, achieving a full set of eight valence electrons signifies chemical stability.

In chlorine-oxygen compounds, the octet rule acts as an indicator of whether the structure is likely stable. For instance, in the Lewis structure of ClO₄⁻, every atom satisfies the octet rule, which means all the atoms have eight electrons associated with them in Lewis representations.

• Chlorine can expand its octet, having more than eight electrons, due to available d-orbitals. This is an exception rather than other elements like carbon, nitrogen, or oxygen.
• In ClO, chlorine does not satisfy the octet rule as it features fewer than eight valence electrons around it, making it less stable according to this rule.

While useful, the octet rule does have exceptions. Particularly in molecules involving atoms from the third period and beyond, like chlorine, expanded octets are possible. This happens because such atoms can utilize d-orbitals to hold additional electrons.

Valence Electrons

Valence electrons are the outermost electrons of an atom and are primarily responsible for an atom’s chemical properties. They determine how atoms will chemically bond with each other to form molecules. Here's a useful breakdown:

• Chlorine has seven valence electrons, making it one electron short of the noble gas configuration.
• Oxygen has six valence electrons, needing two more to complete its octet.

When forming bonds, these atoms will share, donate, or accept electrons to achieve a stable electron configuration, usually of a filled outer shell.

For polyatomic ions like ClO₄⁻, the number of valence electrons includes additional electrons corresponding to the ion's charge. The negative charge in ions like ClO₄⁻ and ClO₂⁻ indicates the presence of one extra electron that contributes to fulfilling the octet in the involved atoms.

Understanding valence electrons helps in drawing Lewis structures, predicting molecule shapes, and explaining the molecule's reactivity tendencies. Knowing the valence electron count is crucial for both predicting the number of bonds an atom can form and for understanding its placement within a molecule.