Which one of the following does not exhibit variable oxidation states?

Options

A. Zn
B. Fe
C. Cu
D. Cr

Answer

To determine which of the following elements does not exhibit variable oxidation states, we will analyze the electronic configurations of each element provided in the question: zinc, iron, copper, and chromium.

### Step-by-Step Solution:

1. **Identify the Elements and Their Atomic Numbers:**
- Zinc (Zn) - Atomic number 30
- Iron (Fe) - Atomic number 26
- Copper (Cu) - Atomic number 29
- Chromium (Cr) - Atomic number 24

2. **Write the Electronic Configurations:**
- **Zinc (Zn)**:
- Atomic number 30:
- Electronic configuration: [Ar] 4s² 3d¹⁰
- **Iron (Fe)**:
- Atomic number 26:
- Electronic configuration: [Ar] 4s² 3d⁶
- **Copper (Cu)**:
- Atomic number 29:
- Electronic configuration: [Ar] 4s¹ 3d¹⁰
- **Chromium (Cr)**:
- Atomic number 24:
- Electronic configuration: [Ar] 4s¹ 3d⁵

3. **Analyze the Electronic Configurations:**
- **Zinc** has a completely filled d-subshell (3d¹⁰) and s-subshell (4s²). This stable configuration makes it less likely to lose electrons and exhibit variable oxidation states.
- **Iron**, **Copper**, and **Chromium** have partially filled d-subshells, which allows them to lose varying numbers of electrons and exhibit different oxidation states.

4. **Conclusion:**
- Among the elements analyzed, **Zinc (Zn)** is the only element that does not exhibit variable oxidation states due to its stable electronic configuration.

### Final Answer:
**Zinc (Zn)** does not exhibit variable oxidation states.

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