The order of reactivity of halogens towards hydrogen is

Options

A. `F_(2) lt Cl_(2) lt Br_(2) lt I_(2)`
B. `I_(2) lt Br_(2) lt Cl_(2) lt F_(2)`
C. `Cl_(2) lt Br_(2) lt I_(2) lt F_(2)`
D. `Br_(2) lt Cl_(2) lt F_(2) lt I_(2)`

Answer

To determine the order of reactivity of halogens towards hydrogen, we need to consider the properties of the halogens and their ability to react with hydrogen. The halogens in question are fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2).

### Step-by-Step Solution:

1. **Identify the Halogens**: The halogens we are considering are F2 (fluorine), Cl2 (chlorine), Br2 (bromine), and I2 (iodine).

2. **Understand Reactivity**: Reactivity in this context refers to how readily these halogens react with hydrogen (H2) to form hydrogen halides (e.g., HF, HCl, HBr, HI).

3. **Consider Electronegativity**: The reactivity of halogens decreases as their electronegativity decreases. Fluorine is the most electronegative element, followed by chlorine, bromine, and iodine.

4. **Analyze Experimental Data**:
- **Fluorine (F2)**: Reacts explosively with hydrogen even in the absence of heat or light.
- **Chlorine (Cl2)**: Reacts explosively with hydrogen but requires heat or light to initiate the reaction.
- **Bromine (Br2)**: Reacts with hydrogen but is less explosive and requires flame to initiate the reaction.
- **Iodine (I2)**: Has a very low reactivity with hydrogen; the reaction does not go to completion and is often at equilibrium.

5. **Establish the Order of Reactivity**: Based on the above analysis, we can establish the order of reactivity towards hydrogen:
- Most reactive: F2
- Next: Cl2
- Then: Br2
- Least reactive: I2

Thus, the order of reactivity of halogens towards hydrogen is:
**F2 > Cl2 > Br2 > I2**

### Final Answer:
The order of reactivity of halogens towards hydrogen is F2 > Cl2 > Br2 > I2.

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