The number of lone pairs of electrons present in central atom of `ClF_3` is:

Answer

To determine the number of lone pairs of electrons present on the central atom of ClF3 (chlorine trifluoride), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Central Atom**:
In ClF3, chlorine (Cl) is the central atom, and it is bonded to three fluorine (F) atoms.

2. **Determine the Valence Electrons of Chlorine**:
Chlorine has an atomic number of 17. Its electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁵. The valence electrons are the electrons in the outermost shell (n=3), which are 3s² 3p⁵. Therefore, chlorine has a total of 7 valence electrons.

3. **Count the Electrons Used in Bonding**:
In ClF3, chlorine forms bonds with three fluorine atoms. Each bond involves one electron from chlorine. Thus, 3 of the 7 valence electrons of chlorine are used to form bonds with the three fluorine atoms.

4. **Calculate Remaining Electrons**:
After using 3 electrons for bonding, we subtract these from the total valence electrons:
\[ 7 \text{ (total valence electrons)} - 3 \text{ (used for bonding)} = 4 \text{ (remaining electrons)} \]

5. **Determine Lone Pairs**:
The remaining 4 electrons on the chlorine atom will exist as lone pairs. Since a lone pair consists of 2 electrons, we can calculate the number of lone pairs:
\[ \frac{4 \text{ (remaining electrons)}}{2} = 2 \text{ (lone pairs)} \]

### Final Answer:
The number of lone pairs of electrons present in the central atom of ClF3 is **2**.

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