Draw the Lewis structure for PO3- including any valid resonance structures. Which of the following statements is TRUE? (A))The PO3 ion contains three identical bonds, all equivalent to 12 bonds. B) The PO3 ion contains one P-0 single bond and two P=O double bonds. C) The PO3 ion contains two P-O single bonds and one P=O double bonds) D) The PO3 ion contains two P-0 single bonds and one P O triple bond. E) None of the above are true.
The Correct Answer and Explanation is :
To answer the question, we need to first draw the Lewis structure of the phosphate ion (PO₃³⁻), including any resonance structures.
Step 1: Count total valence electrons:
- Phosphorus (P) is in Group 15, so it has 5 valence electrons.
- Oxygen (O) is in Group 16, so each oxygen atom has 6 valence electrons.
- The ion has a 3- charge, which means it has gained 3 extra electrons.
Total valence electrons = 5 (from P) + 3 × 6 (from O) + 3 (extra electrons) = 24 valence electrons.
Step 2: Draw the basic structure:
The phosphorus atom is in the center with three oxygen atoms surrounding it. Place single bonds between phosphorus and oxygen, each bond contributing 2 electrons.
The initial structure looks like this:
O
|
O—P—O
|
OWe have used 6 electrons (3 bonds × 2 electrons each) from the total 24, leaving us with 18 electrons to distribute.
Step 3: Distribute the remaining electrons:
Next, we place lone pairs on the oxygen atoms. Each oxygen atom will take 6 electrons to complete its octet. The remaining 6 electrons will be placed on phosphorus, making it less stable. So, phosphorus will form double bonds with some oxygen atoms.
Step 4: Form resonance structures:
To satisfy the octet rule for oxygen atoms and minimize formal charges, we can form resonance structures. We create multiple valid structures where the bonds between phosphorus and oxygen may switch between single and double bonds, thus making the structure more stable.
Lewis Structure:
The most common resonance structures show that there are two single bonds (P–O) and one double bond (P=O). The oxygen atoms with single bonds will have a negative formal charge, and the phosphorus will have a formal charge of +1 to balance the 3- charge of the ion.
Answer:
The correct answer is C) The PO₃ ion contains two P-O single bonds and one P=O double bond.
Explanation:
- The phosphate ion (PO₃³⁻) has a resonance structure, where one of the bonds between phosphorus and oxygen is a double bond, and the other two are single bonds. This creates a formal negative charge on two of the oxygen atoms.
- The central phosphorus atom is involved in bonding with oxygen through both single and double bonds. The charges are distributed across the structure in a way that maintains the overall 3- charge.
- A) is incorrect because the bonds are not identical to each other due to resonance.
- B) is incorrect because it suggests that the structure has one P–O single bond and two P=O double bonds, which is not the case.
- D) is incorrect because there is no P–O triple bond in the ion.
- E) is incorrect because statement C is true.
Thus, the true statement about the phosphate ion is C.