Which of the following has been arrange in order of detereasing dipole moment?

Options

A. `CH_(3)CI gt CH_(3)F gt CH_(3)Br gt CH_(3)I`
B. `CH_(3)F gt CH_(3)CI gt CH_(3)Br gt CH_(3)I`
C. `CH_(3)CI gt CH_(3)Br gt CH_(3)I gt CH_(3)F`
D. `CH_(3)F gt CH_(3)CI gt CH_(3)I gt CH_(3)Br`

Explanation

To determine the order of decreasing dipole moment for the compounds CH3Cl, CH3F, CH3Br, and CH3I, we can follow these steps:

### Step 1: Understand Dipole Moment
The dipole moment of a molecule is a measure of the separation of positive and negative charges in the molecule. It depends on two main factors: the electronegativity of the atoms involved and the distance between them.

### Step 2: Identify the Electronegativity of Atoms
The electronegativities of the halogens are as follows:
- Fluorine (F): 4.0
- Chlorine (Cl): 3.0
- Bromine (Br): 2.8
- Iodine (I): 2.5

### Step 3: Analyze the Compounds
The compounds we are analyzing are:
- CH3F
- CH3Cl
- CH3Br
- CH3I

### Step 4: Compare Electronegativity and Bond Length
1. **CH3F**: Highest electronegativity (F) leads to the strongest dipole moment.
2. **CH3Cl**: Chlorine has lower electronegativity than fluorine, but the bond length is longer than that of CH3F, which reduces the dipole moment compared to CH3F.
3. **CH3Br**: Bromine has even lower electronegativity than chlorine, resulting in a smaller dipole moment than CH3Cl.
4. **CH3I**: Iodine has the lowest electronegativity among these halogens, leading to the smallest dipole moment.

### Step 5: Order the Compounds
Based on the above analysis, we can arrange the compounds in order of decreasing dipole moment:
1. **CH3F** (highest dipole moment)
2. **CH3Cl**
3. **CH3Br**
4. **CH3I** (lowest dipole moment)

### Final Answer
The order of decreasing dipole moment is:
**CH3F > CH3Cl > CH3Br > CH3I**