The order of reactivity of halogens with methane is 

Options

A. `F_2 lt Cl_2 lt Br_2 lt I_2`
B. `F_2 gt Cl_2 gt Br_2 gt I_2`
C. `F_2 lt Br_2 lt Cl_2 lt I_2`
D. `F_2 lt I_2 lt Br_2 lt Cl_2`

Answer

To determine the order of reactivity of halogens with methane, we need to analyze the reactivity of each halogen (fluorine, chlorine, bromine, and iodine) with methane.

### Step-by-Step Solution:

1. **Understanding Reactivity with Methane**:
- Methane (CH₄) can react with halogens through a substitution reaction, where hydrogen atoms are replaced by halogen atoms.

2. **Reactivity of Fluorine**:
- Fluorine (F₂) is the most reactive halogen. It reacts explosively with methane, leading to the complete substitution of all four hydrogen atoms, forming carbon (C) and hydrogen fluoride (HF).
- Reaction: CH₄ + 4F₂ → C + 4HF
- This indicates that fluorine is highly reactive towards methane.

3. **Reactivity of Chlorine**:
- Chlorine (Cl₂) reacts with methane but requires the presence of heat or light to initiate the reaction. The reaction produces various substitution products such as chloromethane (CH₃Cl), dichloromethane (CH₂Cl₂), trichloromethane (CHCl₃), and carbon tetrachloride (CCl₄).
- This shows that chlorine is less reactive than fluorine but still significantly reactive.

4. **Reactivity of Bromine**:
- Bromine (Br₂) reacts with methane more slowly than chlorine. It also produces similar substitution products but at a much slower rate.
- This indicates that bromine is less reactive than chlorine.

5. **Reactivity of Iodine**:
- Iodine (I₂) has very little reactivity with methane under normal conditions. It does not react unless an oxidizing agent is present.
- This shows that iodine is the least reactive halogen towards methane.

6. **Order of Reactivity**:
- Based on the analysis, we can conclude the order of reactivity of halogens with methane is:
- Fluorine > Chlorine > Bromine > Iodine

### Final Answer:
The order of reactivity of halogens with methane is: **Fluorine > Chlorine > Bromine > Iodine**.

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