Correct Option
Fluorine (F₂) is the most reactive element among the halogens. This high reactivity is attributed to several factors:
- It possesses the highest electronegativity (3.98 on the Pauling scale) among all elements.
- It has a low F-F bond dissociation energy, meaning relatively little energy is required to break the diatomic fluorine molecule.
- It exhibits a high electron affinity, indicating a strong tendency to gain an electron and form a stable fluoride ion (F⁻).
These combined properties make fluorine highly reactive, enabling it to react even with noble gases like xenon under specific conditions.
Incorrect Options
The reactivity of halogens generally decreases down the group from fluorine to iodine. This trend is primarily due to the increasing atomic size, decreasing electronegativity, and increasing bond dissociation energy of the diatomic halogen molecules as one moves down the group.
- Chlorine (b) is reactive but less so than fluorine. Its electronegativity is lower, and its Cl-Cl bond dissociation energy is higher compared to fluorine.
- Bromine (c) is less reactive than chlorine, further illustrating the decreasing reactivity down the group.
- Iodine (d) is the least reactive among the given halogens, consistent with its position at the bottom of the group.