Among the halogens, fluorine differs considerably form the other members. The hydrides of halogens also differ in their properties.
Florine differs form the order halogens due to:

Options

A. Small size
B. Very high electronegativity
C. Non-availability of d-orbitals
D. All of these

Answer

To understand why fluorine differs considerably from the other halogens, we need to analyze several key factors related to its atomic structure and properties. Let's break it down step by step:

### Step 1: Atomic Size
- **Fluorine has a small atomic size** compared to other halogens (chlorine, bromine, iodine). As we move down the group in the periodic table, the atomic size increases due to the addition of electron shells.
- **Reason**: Fluorine is in the second period of the periodic table, while the other halogens are in the third and fourth periods, leading to larger atomic radii for chlorine, bromine, and iodine.

### Step 2: Electronegativity
- **Fluorine has the highest electronegativity** of all elements, with a value of 4.0 on the Pauling scale. This means fluorine has a strong tendency to attract electrons towards itself when forming bonds.
- **Reason**: The small size of fluorine allows it to exert a stronger pull on the bonding electrons compared to larger halogens.

### Step 3: Availability of d-Orbitals
- **Fluorine does not have vacant d-orbitals**, while chlorine, bromine, and iodine do. This absence of d-orbitals in fluorine affects its bonding and chemical behavior.
- **Reason**: Fluorine is in the second period, where only s and p orbitals are present, whereas the heavier halogens have d-orbitals available for bonding and can exhibit different coordination numbers and oxidation states.

### Step 4: Summary of Differences
- **Fluorine is unique among the halogens** due to its small size, high electronegativity, and the absence of d-orbitals. These factors contribute to its distinct chemical properties compared to chlorine, bromine, and iodine.

### Conclusion
- Therefore, the correct answer to why fluorine differs from the other halogens is that it has a small size, high electronegativity, and no available d-orbitals, making the option "all of these" (option 4) the correct choice.

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