How many equivalent resonance structures can be drawn for the perchlorate ion, ClO_4^-?

• A. 1
• B. 2
• C. 3
• D. 4

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the structure of the perchlorate ion, ClO_4^-. It consists of one chlorine atom centrally bonded to four oxygen atoms, with an overall charge of -1.
2. Step 2: Recognize that resonance structures involve different ways of arranging double bonds and lone pairs without changing the positions of atoms. For ClO_4^-, the resonance arises from the placement of double bonds between chlorine and oxygen atoms.
3. Step 3: Draw the Lewis structure with one Cl=O double bond and three Cl–O single bonds, assigning formal charges accordingly to satisfy the octet rule and overall charge.
4. Step 4: Generate equivalent resonance structures by moving the double bond to each of the other three oxygen atoms in turn, while keeping the rest of the structure the same. Each structure will have one double bond and three single bonds, with the negative charge distributed over the oxygens.
5. Step 5: Count all unique resonance structures formed by placing the double bond on each of the four oxygen atoms, resulting in a total of 4 equivalent resonance structures.