How many lone pairs are present in white phosphorous ?

Explanation

To determine the number of lone pairs present in white phosphorus (P4), we can follow these steps:

### Step 1: Understand the Structure of White Phosphorus
White phosphorus consists of four phosphorus atoms (P4) arranged in a tetrahedral structure. Each phosphorus atom is bonded to three other phosphorus atoms.

**Hint:** Recall the molecular structure of white phosphorus and how atoms are arranged in a tetrahedral shape.

### Step 2: Determine the Valence Electrons of Phosphorus
Phosphorus has five valence electrons. In the tetrahedral structure of white phosphorus, each phosphorus atom forms three single bonds with neighboring phosphorus atoms.

**Hint:** Remember that the number of valence electrons can be found using the periodic table.

### Step 3: Calculate the Electrons Used in Bonding
Since each phosphorus atom forms three bonds, it uses three of its five valence electrons for bonding. This leaves two electrons remaining.

**Hint:** Consider how many electrons are involved in bonding and how many are left over.

### Step 4: Identify the Lone Pairs
The two remaining electrons on each phosphorus atom constitute one lone pair. Since there are four phosphorus atoms in white phosphorus, we can calculate the total number of lone pairs.

**Hint:** Think about how many lone pairs each atom contributes to the total.

### Step 5: Calculate the Total Number of Lone Pairs
Since each of the four phosphorus atoms has one lone pair, the total number of lone pairs in white phosphorus is:
\[ \text{Total lone pairs} = 4 \text{ (one from each phosphorus atom)} \]

**Hint:** Add up the lone pairs contributed by each atom to find the total.

### Final Answer
The total number of lone pairs present in white phosphorus is **4**.

---