The formal charge on P on the phosphonium ion `(PH_(4)^(+))` is :

Options

A. `-1`
B. `+5`
C. `0`
D. `+1`

Answer

To determine the formal charge on phosphorus in the phosphonium ion \( \text{PH}_4^+ \), we can follow these steps:

### Step 1: Identify the Valence Electrons
Phosphorus (P) is in group 15 of the periodic table, which means it has 5 valence electrons. Each hydrogen (H) atom has 1 valence electron.

### Step 2: Count the Total Electrons in the Ion
In the phosphonium ion \( \text{PH}_4^+ \):
- There are 4 hydrogen atoms, contributing a total of \( 4 \times 1 = 4 \) electrons.
- Therefore, the total number of valence electrons in the ion is \( 5 + 4 = 9 \).

### Step 3: Determine the Electron Configuration
In \( \text{PH}_4^+ \):
- Phosphorus forms 4 bonds with the 4 hydrogen atoms.
- Each bond consists of 2 electrons, so there are \( 4 \times 2 = 8 \) shared electrons.
- Phosphorus donates its lone pair (2 electrons) to form a bond with one of the hydrogen atoms.

### Step 4: Calculate Non-bonding Electrons
In \( \text{PH}_4^+ \):
- Phosphorus has no non-bonding (lone pair) electrons left after forming bonds with the hydrogen atoms.

### Step 5: Apply the Formal Charge Formula
The formal charge (FC) can be calculated using the formula:
\[ \text{FC} = \text{Valence Electrons} - \text{Non-bonding Electrons} - \frac{1}{2} \times \text{Bonding Electrons} \]
Substituting the values:
- Valence Electrons (P) = 5
- Non-bonding Electrons = 0
- Bonding Electrons = 8 (from 4 bonds)

\[ \text{FC} = 5 - 0 - \frac{1}{2} \times 8 \]
\[ \text{FC} = 5 - 0 - 4 = +1 \]

### Conclusion
The formal charge on phosphorus in the phosphonium ion \( \text{PH}_4^+ \) is \( +1 \).

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