Which element in the given below does not show variable valency ?

Options

A. Zn
B. Cu
C. Ni
D. Mn

Answer

To determine which element does not show variable valency among the given options, we will analyze the valency of each element mentioned in the video transcript.

### Step-by-step Solution:

1. **Understanding Variable Valency**:
- Variable valency refers to the ability of an element to exhibit more than one oxidation state or valency in its compounds. For example, elements like iron (Fe) can show +2 and +3 oxidation states.

2. **Analyzing the Elements**:
- The elements mentioned in the transcript are Zinc (Zn), Copper (Cu), and Manganese (Mn).

3. **Zinc (Zn)**:
- Zinc typically exhibits a valency of +2 in its compounds. It does not show variable valency because it does not have stable oxidation states other than +2 (except in its free state where it has a valency of 0). Therefore, it has only one common valency in compounds.

4. **Copper (Cu)**:
- Copper can exhibit multiple oxidation states, primarily +1 and +2. This means it shows variable valency.

5. **Manganese (Mn)**:
- Manganese can show several oxidation states, including +1, +2, +3, +4, +6, and +7. Thus, it also exhibits variable valency.

6. **Conclusion**:
- Among the elements discussed, only Zinc (Zn) does not show variable valency, as it predominantly exists in the +2 oxidation state in compounds.

### Final Answer:
**Zinc (Zn)** does not show variable valency.