Calculate the value of " x+y-z" here x,y and z are total number of non-bonded electron pair (s),pie `(pi)` bond(s) and sigma `(sigma)` bonds in hydrogen phosphite ion respectively.

Explanation

To solve the problem of calculating the value of \( x + y - z \) for the hydrogen phosphite ion, we will follow these steps:

### Step 1: Identify the components
- **x**: Total number of non-bonded electron pairs (lone pairs).
- **y**: Total number of pi bonds.
- **z**: Total number of sigma bonds.

### Step 2: Draw the Lewis structure of the hydrogen phosphite ion (\( H_2PO_3^- \))
1. The central atom is phosphorus (P).
2. Phosphorus is bonded to three oxygen atoms and one hydrogen atom.
3. One of the oxygen atoms is double-bonded to phosphorus, while the other two are single-bonded (one of which carries a negative charge).

### Step 3: Count the lone pairs (x)
- Each oxygen atom typically has 6 valence electrons.
- In the Lewis structure:
- The double-bonded oxygen has 2 lone pairs.
- The negatively charged oxygen has 3 lone pairs.
- The other oxygen (single-bonded) has 2 lone pairs.
- Total lone pairs:
- Double-bonded oxygen: 2 lone pairs
- Single-bonded oxygen (with negative charge): 3 lone pairs
- Single-bonded oxygen: 2 lone pairs
- Total \( x = 2 + 3 + 2 = 7 \) lone pairs.

### Step 4: Count the pi bonds (y)
- A pi bond is formed in addition to a sigma bond when there is a double bond.
- In the hydrogen phosphite ion, there is one double bond (between phosphorus and one oxygen).
- Thus, \( y = 1 \).

### Step 5: Count the sigma bonds (z)
- Each single bond is a sigma bond, and the first bond in a double bond is also a sigma bond.
- In the hydrogen phosphite ion:
- There are 3 single bonds (P-O, P-O, and P-H).
- There is 1 double bond (P=O), which contributes 1 sigma bond.
- Total sigma bonds:
- 3 (from single bonds) + 1 (from double bond) = 4 sigma bonds.
- Thus, \( z = 4 \).

### Step 6: Calculate \( x + y - z \)
- Substitute the values:
- \( x = 7 \)
- \( y = 1 \)
- \( z = 4 \)
- Therefore, \( x + y - z = 7 + 1 - 4 = 4 \).

### Final Answer
The value of \( x + y - z \) is **4**.

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