Polar covalent molecules exhibit dipole moment. Dipole moment is equal to the product of charge separation , q and the bond length d for the bond. Unit of dipole moment is debye. One debye is equal to `10^(-18)` esu cm.
Dipole moments is a vector quantity. It has both magnitude and direction. Hence, dipole moment of a molecule depends upon the relative orientation of the bond dipoles, but not on the polarity of bonds alone. A symmetrical structure shows zero dipole moment. Thus, dipole moment helps to predict the geometry of a molecules. Dipole moment values can be distinguish between cis- and trans- isomers, ortho, meta and pare-forms of a substance, etc.
Q. Which is a polar molecule?

Options

A. `XeF_(4)`
B. `BF_(3)`
C. `I_(2)Cl_(6)`
D. `PCl_(2)F_(3)`

Explanation

To determine which of the given molecules is a polar molecule, we need to analyze the dipole moments of each molecule based on their structures and the arrangement of their bonds. Here’s a step-by-step solution:

### Step 1: Understand the concept of dipole moment
The dipole moment (\( \mu \)) of a molecule is defined as the product of the charge separation (\( q \)) and the bond length (\( d \)). It is a vector quantity, meaning it has both magnitude and direction. A molecule is considered polar if it has a non-zero dipole moment.

### Step 2: Analyze the given molecules
We will analyze the dipole moments of the following molecules:
1. **XeF4 (Xenon Tetrafluoride)**
2. **BF3 (Boron Trifluoride)**
3. **I2Cl6 (Diiodine Hexachloride)**
4. **PCl2F3 (Phosphorus Dichloride Trifluoride)**

### Step 3: Determine the polarity of each molecule

#### 1. **XeF4**
- Structure: The molecule has a square planar geometry due to the presence of two lone pairs on xenon.
- Analysis: The dipole moments of the four fluorine atoms are equal in magnitude but opposite in direction, effectively canceling each other out. Thus, the overall dipole moment is zero.
- Conclusion: **Non-polar**

#### 2. **BF3**
- Structure: The molecule has a trigonal planar geometry.
- Analysis: The three fluorine atoms are symmetrically arranged around the boron atom. The dipole moments of the fluorine atoms also cancel each other out.
- Conclusion: **Non-polar**

#### 3. **I2Cl6**
- Structure: The molecule has a complex structure with iodine and chlorine atoms arranged in a way that the dipole moments of the chlorine atoms cancel out.
- Analysis: The arrangement of chlorine atoms leads to the cancellation of dipole moments.
- Conclusion: **Non-polar**

#### 4. **PCl2F3**
- Structure: The molecule has a trigonal bipyramidal geometry with two chlorine atoms in the equatorial position and three fluorine atoms in the axial position.
- Analysis: The electronegativity of fluorine is greater than that of chlorine, leading to a net dipole moment directed towards the fluorine atoms. The dipole moments do not cancel out.
- Conclusion: **Polar**

### Final Answer
The polar molecule among the given options is **PCl2F3**.

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