Fluorine, the first member of group 17, differs form the other members of group in may respects due to:
i. Very small size
ii. Very high electronegativity
iii. Absence of vacant d-orbitals in the valence shell
iv. Dissociation energy in the molecular form `(X_(2))` is the least
Which member of the group 17 does not show positive oxidation state ?

Options

A. Iodine
B. Bromine
C. Chlorine
D. Fluorine

Answer

To solve the question, we need to analyze the characteristics of Fluorine and the other members of Group 17 (the halogens) and determine which member does not exhibit a positive oxidation state.

### Step-by-Step Solution:

1. **Understand the Characteristics of Fluorine**:
- Fluorine is the first member of Group 17 and is known for its very small atomic size and very high electronegativity.
- It has no vacant d-orbitals in its valence shell, which is a significant difference from the heavier halogens (like Chlorine, Bromine, and Iodine).
- Fluorine has the highest dissociation energy in its molecular form (F2) compared to other halogens.

2. **Identify the Oxidation States of Halogens**:
- Halogens can exhibit various oxidation states.
- Fluorine primarily shows a -1 oxidation state because it readily gains one electron to achieve a stable electronic configuration.
- Other halogens like Chlorine, Bromine, and Iodine can show positive oxidation states (e.g., +1, +3, +5, +7) in addition to their -1 oxidation state.

3. **Determine Which Halogen Does Not Show Positive Oxidation State**:
- Since Fluorine is highly electronegative and has a very small size, it does not lose electrons and thus does not exhibit a positive oxidation state.
- Therefore, the answer to the question is Fluorine.

### Conclusion:
The member of Group 17 that does not show a positive oxidation state is **Fluorine**.