Oxidation number of P in `PO_4^(3-)` ion is :

Options

A. `-3`
B. `+7`
C. `+5`
D. `+3`

Answer

To find the oxidation number of phosphorus (P) in the phosphate ion \( PO_4^{3-} \), we can use the following step-by-step method:

### Step 1: Assign Variables
Let the oxidation number of phosphorus be \( x \).

### Step 2: Determine the Oxidation Number of Oxygen
The oxidation number of oxygen (O) is typically \(-2\). Since there are 4 oxygen atoms in \( PO_4^{3-} \), we can calculate the total contribution from oxygen:
\[ \text{Total oxidation number from oxygen} = 4 \times (-2) = -8 \]

### Step 3: Set Up the Equation
The overall charge of the phosphate ion is \(-3\). Therefore, we can set up the equation based on the sum of the oxidation numbers:
\[ x + (-8) = -3 \]

### Step 4: Solve for \( x \)
Now, we can solve the equation for \( x \):
\[ x - 8 = -3 \]
\[ x = -3 + 8 \]
\[ x = +5 \]

### Conclusion
The oxidation number of phosphorus in the \( PO_4^{3-} \) ion is \( +5 \).

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