The halogens have the smallest atomic radii in their respective periods. The atomic radius of fluorine is extremely small. All halogens exhibit -1 oxidation state. They are strong oxidising agents and have maximum negative electron gain enthalpy. Among halogens, fluorine shows anomalous behaviour in many properties: For example electronegativity and ionisation enthalpy are higher for fluorine than expected whereas bond dissociation enthalpy, m.p. and b.p.and electron gain enthalpy are quite lower than expected. Halogens react with hydrogen to give hydrogen halides (HX) and combine amongst themselves to form a number of compounds of the type `XX', XX'_(3), XX'_(5)` and `XX'_(7)` called inter halogens.
Why fluorine shows anomalous behaviour as compared to other halogens?

Explanation

To explain why fluorine shows anomalous behavior compared to other halogens, we can break down the reasoning into several key points:

### Step-by-Step Solution:

1. **Position in the Periodic Table**:
- Fluorine is the first element in the halogen group (Group 17) of the periodic table. Being the lightest halogen, it has unique properties compared to its heavier counterparts (chlorine, bromine, iodine, and astatine).

**Hint**: Consider how the position of an element in the periodic table influences its properties.
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