In `PO_(4)^(3-)` ion, the effective charge on each oxygen atom and P-O bond order respectively are

Options

A. `-0.75, 1.25`
B. `-0.75 , 1.0`
C. `-0.75 , 0.6`
D. `-3, 1.25`

Answer

To determine the effective charge on each oxygen atom and the bond order of the P-O bond in the \( PO_4^{3-} \) ion, we can follow these steps:

### Step 1: Draw the Lewis Structure
1. **Count the total number of valence electrons**:
- Phosphorus (P) has 5 valence electrons.
- Each oxygen (O) has 6 valence electrons, and there are 4 oxygens.
- The ion has a charge of -3, which means we add 3 more electrons.
- Total = \( 5 + (4 \times 6) + 3 = 5 + 24 + 3 = 32 \) valence electrons.

2. **Arrange the atoms**:
- Place phosphorus in the center and surround it with four oxygen atoms.

3. **Distribute the electrons**:
- Start by forming single bonds between P and each O. This uses 8 electrons (4 bonds).
- Distribute the remaining electrons to satisfy the octet rule for oxygen.

4. **Form double bonds**:
- To minimize formal charges, we can form one double bond between P and one O, while the other three O atoms will carry a negative charge.

### Step 2: Calculate the Effective Charge on Each Oxygen Atom
1. **Identify the charges**:
- In the structure, one oxygen is double bonded to phosphorus (neutral) and the other three oxygens are single bonded with a -1 charge each.

2. **Distribute the total charge**:
- The total negative charge of -3 is distributed among the four oxygen atoms.
- The charge on the double-bonded oxygen is 0, while the three single-bonded oxygens each have a charge of -1.

3. **Calculate the effective charge**:
- The effective charge on each of the three negatively charged oxygens is \( -1 \).
- The effective charge on the double-bonded oxygen is \( 0 \).

### Step 3: Calculate the Bond Order
1. **Identify the bonds**:
- In the Lewis structure, we have one P=O double bond and three P-O single bonds.

2. **Count the total number of bonds**:
- There are 5 bonds in total: 1 double bond (counted as 2) and 3 single bonds (counted as 3).

3. **Determine the number of resonating structures**:
- The resonance structures can be drawn by moving the double bond among the four oxygen atoms. There are 4 main resonance structures.

4. **Calculate the bond order**:
- Bond order is calculated using the formula:
\[ \text{Bond Order} = \frac{\text{Number of bonds in conjugation}}{\text{Total number of resonating structures}} = \frac{5}{4} = 1.25 \]

### Final Answers
- The effective charge on each oxygen atom is:
- For three oxygens: -1
- For one oxygen: 0
- The bond order of the P-O bond is 1.25.