The order of the oxidation state of the phos- phorus atom in `H_3PO_2, H_3PO_4 , H_3PO_3` and `H_4P_2O_6` is : -

Options

A. `H_3PO_4 gt H_3PO_2 gt H_3PO_3 gt H_4P_2O_6`
B. `H_3PO_2 gt H_3PO_3 gt H_4P_2O_6 gt H_3PO_4`
C. `H_3PO_3 gt H_3PO_2 gt H_3PO_4 gt H_4P_2O_6`
D. `H_3PO_4 gt H_4P_2O_6 gt H_3PO_3 gt H_3PO_2`

Answer

To find the order of the oxidation state of the phosphorus atom in the compounds \( H_3PO_2 \), \( H_3PO_4 \), \( H_3PO_3 \), and \( H_4P_2O_6 \), we will calculate the oxidation state of phosphorus in each compound step by step.

### Step 1: Calculate the oxidation state of phosphorus in \( H_3PO_2 \)

1. **Identify the structure**: \( H_3PO_2 \) is known as Hypophosphorous Acid. It contains one phosphorus atom bonded to two hydroxyl groups (OH) and one double-bonded oxygen (O).
2. **Assign oxidation states**:
- Each oxygen (O) in the double bond contributes -2.
- Each hydroxyl group (OH) contributes -1.
- Each hydrogen (H) contributes +1.
3. **Set up the equation**:
\[ x + 2(-1) + 1 + 1 = 0 \]
where \( x \) is the oxidation state of phosphorus.
4. **Solve for \( x \)**:
\[ x - 2 + 2 = 0 \implies x = +1 \]

### Step 2: Calculate the oxidation state of phosphorus in \( H_3PO_4 \)

1. **Identify the structure**: \( H_3PO_4 \) is Phosphoric Acid. It has one phosphorus atom bonded to four oxygen atoms (one double-bonded and three single-bonded to hydroxyl groups).
2. **Assign oxidation states**:
- The double-bonded oxygen contributes -2.
- Each hydroxyl group contributes -1.
3. **Set up the equation**:
\[ x + 4(-2) + 3(+1) = 0 \]
4. **Solve for \( x \)**:
\[ x - 8 + 3 = 0 \implies x = +5 \]

### Step 3: Calculate the oxidation state of phosphorus in \( H_3PO_3 \)

1. **Identify the structure**: \( H_3PO_3 \) is Orthophosphorous Acid. It has one phosphorus atom bonded to three oxygen atoms (one double-bonded and two single-bonded to hydroxyl groups).
2. **Assign oxidation states**:
- The double-bonded oxygen contributes -2.
- Each hydroxyl group contributes -1.
3. **Set up the equation**:
\[ x + 2(-1) + 1 + 1 = 0 \]
4. **Solve for \( x \)**:
\[ x - 2 + 2 = 0 \implies x = +3 \]

### Step 4: Calculate the oxidation state of phosphorus in \( H_4P_2O_6 \)

1. **Identify the structure**: \( H_4P_2O_6 \) is Hypophosphoric Acid. It contains two phosphorus atoms.
2. **Assign oxidation states**:
- Each oxygen contributes -2.
- Each hydroxyl group contributes -1.
3. **Set up the equation**:
\[ 2x + 6(-2) + 4(+1) = 0 \]
4. **Solve for \( x \)**:
\[ 2x - 12 + 4 = 0 \implies 2x - 8 = 0 \implies x = +4 \]

### Summary of Oxidation States:
- \( H_3PO_2 \): +1
- \( H_3PO_3 \): +3
- \( H_4P_2O_6 \): +4
- \( H_3PO_4 \): +5

### Final Order:
The order of oxidation states of phosphorus in the compounds is:
\[ H_3PO_2 < H_3PO_3 < H_4P_2O_6 < H_3PO_4 \]