Halogens exist in `-1, +1, +3, +5 and +7` oxidation states. The halogen that exists only `-1` state is

Options

A. I
B. Br
C. F
D. Cl

Answer

To solve the question regarding which halogen exists only in the -1 oxidation state, we can follow these steps:

### Step 1: Understand the Oxidation States of Halogens
Halogens can exhibit various oxidation states, specifically -1, +1, +3, +5, and +7. This is due to their ability to gain or lose electrons.

**Hint:** Recall that oxidation states indicate the degree of oxidation of an atom in a compound.

### Step 2: Identify the Halogens
The halogens include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). Each of these elements has different properties and capabilities regarding their oxidation states.

**Hint:** List the halogens and consider their electronic configurations.

### Step 3: Analyze Fluorine
Fluorine is the most electronegative element and has an atomic number of 9. It has no d-orbitals in its valence shell, which limits its ability to expand its octet. Therefore, fluorine can only achieve a -1 oxidation state by gaining one electron.

**Hint:** Consider the electronic configuration of fluorine and its electronegativity.

### Step 4: Analyze Other Halogens
Chlorine, bromine, and iodine have d-orbitals available in their valence shells. This allows them to expand their octet and exhibit multiple oxidation states, including +1, +3, +5, and +7.

**Hint:** Compare the electronic configurations of chlorine, bromine, and iodine to fluorine.

### Step 5: Conclusion
Since fluorine can only exist in the -1 oxidation state and does not have the ability to expand its octet due to the absence of d-orbitals, it is the only halogen that exists solely in the -1 oxidation state.

**Final Answer:** The halogen that exists only in the -1 oxidation state is **fluorine (F)**.

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