We can draw three inequivalent Lewis structures for the chlorate ion, ClO3-.

We can draw three inequivalent Lewis structures for the chlorate ion, ClO3-. The concepts of formal charge and electronegativity can help us choose the structure that is the best representation. 1. Assign formal charges to the elements in each of the structures below. Note: Count oxygen as -2 and hydrogen as +1 from the left for each structure. Structure 1: Cl: 0 O: -1 O: -1 O: -1 Structure 2: Cl: 0 O: 0 O: -2 O: +1 Structure 3: Cl: 0 O: -1 O: -1 O: -1

The Correct Answer and Explanation is:

To determine the best Lewis structure for the chlorate ion (ClO₃⁻), we must examine the formal charges on each atom in the possible structures and consider electronegativity.

Step 1: Understanding the Structures

We are given three possible structures for ClO₃⁻, and each structure has its own set of formal charges:

• Structure 1:
  Cl: 0
  O: -1
  O: -1
  O: -1
• Structure 2:
  Cl: 0
  O: 0
  O: -2
  O: +1
• Structure 3:
  Cl: 0
  O: -1
  O: -1
  O: -1

Note: Structure 1 and Structure 3 have identical formal charges.

Step 2: Formal Charge Evaluation

Formal charge is calculated using the formula:
Formal charge = (valence electrons) – (nonbonding electrons + ½ bonding electrons)

The goal is to find the structure where:

1. The formal charges are closest to zero.
2. Any negative charges are on the most electronegative atoms (oxygen is more electronegative than chlorine).

In Structure 1 and Structure 3, each oxygen carries a -1 formal charge, and chlorine is neutral. The total charge is -3, but ClO₃⁻ only has an overall -1 charge. So this structure suggests an over-distribution of negative charge.

In Structure 2, oxygen atoms have formal charges of 0, -2, and +1. This creates a larger separation of charge. Most importantly, there is a +1 charge on oxygen, which is highly unfavorable because oxygen is highly electronegative and rarely carries a positive formal charge.

Step 3: Best Representation

Structure 2 is least likely to represent the chlorate ion well due to the +1 formal charge on oxygen and uneven charge distribution.
Structures 1 and 3 are equivalent and distribute the -1 charge more reasonably among the oxygen atoms.

Conclusion:
The best Lewis structure for ClO₃⁻ is Structure 1 or Structure 3, because:

• The formal charges are more evenly distributed.
• All the negative charges are on oxygen, the more electronegative atom.
• Chlorine has a formal charge of 0, making it a stable configuration.

Thus, Structure 1 (or 3) best represents the chlorate ion.