Two classmates propose different Lewis diagrams for the chlorate ion, ClO₃⁻
CHEMISTRY · Multi-part · AP · Chemistry · Compound Structure and Properties · Compound Structure and Properties
Problem
Two classmates propose different Lewis diagrams for the chlorate ion, ClO₃⁻. Their verbal descriptions are given below.
Diagram I:
• Central chlorine atom with three single bonds, one to each oxygen.
• Two lone pairs on the chlorine.
• Each oxygen bears three lone pairs.
• A negative formal charge is placed on the chlorine.
Diagram II:
• Central chlorine atom with one double bond to an oxygen and two single bonds to the remaining oxygens.
• One lone pair on the chlorine.
• The doubly bonded oxygen has two lone pairs; each singly bonded oxygen has three lone pairs and carries a negative formal charge.
Respond to the prompts that follow.
(a) For each diagram, calculate the formal charge on the central chlorine atom and on one of the singly bonded oxygens, showing your reasoning.
(b) Indicate which diagram more accurately represents the chlorate ion. Justify your choice by referring to both the octet rule (or its applicable exceptions) and the distribution of formal charges.
(c) Draw one additional resonance structure that is equivalent to the preferred diagram in part (b), and explain why resonance is necessary for a complete description of ClO₃⁻.