One of the following has both positive and negative oxidation states

Options

A. Fe
B. Cl
C. He
D. Na

Explanation

To determine which of the given elements has both positive and negative oxidation states, we will analyze the oxidation states of each element: iron (Fe), chlorine (Cl), helium (He), and sodium (Na).

### Step 1: Analyze Iron (Fe)
- **Electronic Configuration**: The electronic configuration of iron is [Ar] 4s² 3d⁶.
- **Oxidation States**:
- If we remove 2 electrons from the 4s orbital, iron can have an oxidation state of +2:
- Configuration becomes [Ar] 3d⁶ (Fe²⁺).
- If we remove one more electron from the 3d orbital, iron can have an oxidation state of +3:
- Configuration becomes [Ar] 3d⁵ (Fe³⁺).
- Iron can also theoretically have a negative oxidation state, but it is less common.

### Step 2: Analyze Chlorine (Cl)
- **Electronic Configuration**: The electronic configuration of chlorine is [Ne] 3s² 3p⁵.
- **Oxidation States**:
- Chlorine can gain one electron to achieve a stable configuration (3s² 3p⁶), resulting in an oxidation state of -1 (Cl⁻).
- If it loses electrons, it can exhibit positive oxidation states:
- Losing one electron gives +1 (Cl⁺).
- Losing two electrons gives +2 (Cl²⁺).
- Losing five electrons gives +5 (Cl⁵⁺).

### Step 3: Analyze Helium (He)
- **Electronic Configuration**: The electronic configuration of helium is 1s².
- **Oxidation States**: Helium is a noble gas and does not typically form compounds. Its oxidation state is generally considered to be 0, and it does not exhibit positive or negative oxidation states.

### Step 4: Analyze Sodium (Na)
- **Electronic Configuration**: The electronic configuration of sodium is [Ne] 3s¹.
- **Oxidation States**: Sodium can lose one electron to achieve a stable configuration, resulting in an oxidation state of +1 (Na⁺). Sodium does not exhibit a negative oxidation state.

### Conclusion:
Among the given elements, **chlorine (Cl)** is the only element that can exhibit both positive (e.g., +1, +2, +5) and negative (-1) oxidation states. Therefore, the answer is:

**Chlorine (Cl)** has both positive and negative oxidation states.

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